Fire detection system

(54) Name: Tree loose ti niormat lons transmission system

The present invention relates to an information transmission device of the type stated in the preamble of claim 1, and in particular relates to the transmission of information, preferably by means of transmission with radlover frequency (RF signal). Such devices are known, for example, from Swedish patent specification 210 'possibly in combination with British patent specification 1 38 ^ 598.

For exemplification, fire detection will be described here.

Transmission systems operating with radio frequency signals are known in relation to fire detection. Such systems use RF10 transmitters, which are individually connected, for example, to an associated heat or smoke level detector, and the transmitters are activated to either an active state or a passive state (determined by the island regarding the construction) when detecting a predetermined change in the prevailing thermal conditions or upon detection of a predetermined smoke intensity. The transmitters are used in conjunction with remote receivers (whereby a single receiver is normally arranged to receive and detect signals from a number of transmitters) and in conjunction with a control or indicator panel included in the same circuit as the receivers. In the typical case, a number of transmitters would be strategically placed on

7506723-1 selected locations on each floor of a multi-storey building, and a receiver would be located on each floor of the building to ^;take signals, which are transmitted from the transmitters on the respective floors. Signals detected by the receivers initiate additional signals, which are transmitted by wires to the common control panel or indicator panel. j!

The transmitters (which include heat or smoke level detectors) are ^in;usually individually powered by dry cell type batteries individually supported by these 1, this allowing: the transmitters to be placed without having to provide electrical wiring (to the transmitters) from any main power source:

In order to achieve faultless operation, fire detection systems must be monitored, which include RF signal transmission. This is achieved tra-; in one of two general ways. The systems are designed an-;

to provide a continuous transmission of RF signals, where an interruption in the transmission indicates either a fire alarm condition \ or a fault of the transmitter, or to provide automatic monitoring | transmission (eg by wireless interrogation signals) of transmitters designed to remain passive under normal conditions:

However, both ways of achieving flawless surgery have inherent problems. Systems that provide continuous signal transmission under normal "conditions" draw a high, continuous current from the transmitter's battery, while systems that use interrogation methods to control the transmitter's working capacity are expensive to manufacture due to the electronic hardware.

These problems can be overcome by arranging the ends to emit periodic monitoring signals and when required;

alarm signals with a different faster repetition frequency. However, it can be predicted that such a simple system will give rise to further problems.

Thus, in the operation of such a system, it is possible and in fact extremely probable that a receiver will receive signals randomly from two or more of a number of transmitters inside and / or outside any building. Under these circumstances, a monitoring signal, which should be detected by the receiver, could be rejected due to simultaneous reception of monitoring signals from more than one transmitter and by interference between these signals. '

This rejection of an otherwise genuine monitoring signal would! be able to result in the receiver giving an incorrect indication of an error;

7506723-1 condition of the transmitter ·

The invention seeks to avoid this problem without resorting to synchronization of the transmitters' signals by providing a system which assumes proper operation of the transmitters in the monitoring mode, if at least one monitoring mode signal is detected before predetermined (successive) time intervals, which are relatively long. to the time periods between successive monitoring mode signals, and which are very long relative to the duration of each monitoring mode signal.

This object is solved by the device according to the invention receiving the characterizing features stated in claim 1. According to the invention, receiving devices are arranged to emit an output signal due to a change in the signal mode in the transmission from the transmitting devices or to emit an output signal if no signal with the duration 6t is detected within each period of successive predetermined error detection periods of the length xt> t, so that the receiving devices emit an alarm indicating output signal, if at least one signal of duration one is received and detected within an alarm detection period of the length / it, therethrough (06 is the time interval between alarm mode signal and monitoring mode signal), which follows a previous signal of the same type, and that the length of the time interval t between successive monitoring mode signals is allowed to operate randomly between each of the transmitting devices.

This makes it possible to take into account the fact that signal interference can give a number of monitoring mode signals which are not detected.

The information transmission system should normally be used in conjunction with a sensing means, which should be arranged to detect the existence of the alarm-inducing state, the sensing means being connected to the transmitter.

Preferably, the alarm mode signals have the same composition as the monitoring mode signals, the only difference between the respective transmissions being in the repetition frequency of the signals. In addition, both types of signals preferably include a pulse train.

Furthermore, the respective alarm mode signals preferably have the same duration (bold) as the monitoring mode signals, the alarm mode signals having a time distance tet (<6h). In this case, the receiver is arranged to provide an alarm indicating output signal, if at least one signal with the duration $ t is received and detected within θη time period (3.t (C <t $ <t), which follows the reception of

7506723-1 a previous such signal.

The invention therefore provides a system which is self-monitoring and which is economical with respect to the transmitter's power consumption. Such an economy is achieved by making the repetition frequency of the monitoring modal signals very low in relation to the repetition frequency of the alarm mode signal.

In addition, the system automatically provides monitoring of the transmitters, since the receivers operate in such a way that they; .

1) detects the monitoring signal - which indicates that the transmitter 10 has normal operation,

2) detects the alarm signal - indicating the presence of an alarm-inducing condition, and

3) detects the absence of any signal - indicating a fault condition, such as a used battery in the transmitter.

As mentioned above, the possibility should be small for an erroneous error indication to be given by the receiver with respect to an associated transmitter; due to the very short period (St) of each monitoring signal pulse train and due to the short time (t) between successive pulse trains relative to the period (xt) allocated for detecting a monitoring mode signal. Thus, it has been mathematically possible to show that for a given area comprising 5000 transmitters, if each transmitter when operating in the monitoring mode generates pulse trains with the frequency one per minute (t), where each pulse train has one. duration of 600yus (St) and with an assumed receiver error detection period (xt) of 10 min, that the probability that one of the transmitters is not properly and uniquely monitored would be 10 ~ $. '

These numerical values ​​are given only to illustrate the very small probability of incorrect monitoring and they should not be considered as representative numerical values ​​for optimal operation.

^ 0 It is probable that the transmission of pulse trains with a duration of. 600 / is would result in a transmission with a bandwidth in excess of that which should be allowed at certain control means. However, substantially the same probability values ​​can be achieved (if the duration of the pulse train * is increased) by reducing the number of transmitters within a given range and / or by increasing the detection period for receiver errors. Alternatively, for some applications of sys. the theme of increasing the likelihood of incorrect monitoring can easily be tolerated. Therefore, with the above in mind, the following (non-limiting) numerical values ​​are given as suitable for the monitoring signal over a

7506723-1 area with several applications of the system:

Duration of each pulse train (St) - 200 jus - 5 ms Pulse train melian space (t) - 30 s - 2 min

Reception error detection period (xt) - 5min - 60 min

In some applications of the system, the pulse train spacing (t) can be significantly increased; for example up to 2 hours. Then the detection period (xt) for receiver error should be adjusted accordingly.

In addition, the following (non-limiting) figures are given as suitable for the alarm signal over an area with different applications of the system:

Duration of each pulse train (St) - 200 / ice - 5 ms Pulse train intervals (St) - 100 jis - 5 ms

Detection period (ö <t) for receiver alarm - 100 yus - 20 sec '' It should be noted that each error detection period, such as

Ί5 it is referred to in the description, may consist of a single time unit, over which any incoming signals are sampled, or a predetermined number of updated (shorter) time units, where sampling is performed during each of such shorter time units. In the latter case, the error detection period will be considered to be composed of the sum of the predetermined number of shorter periods.

In a system with a number of transmitters belonging to any receiver (where the receiver is arranged to distinguish between the addresses of the respective transmitters), the pulse train distance (t) should not .... be fixed as between the respective transmitters. Instead, the value should be ti :::;:;.

allowed to operate randomly (within reasonable limits) in each transmitter. to substantially reduce the possibility of (synchronized) interference between signals transmitted from the transmitters.

The nature or construction of the sensing means, as mentioned above, will depend on the application of the transmission system. In addition to fire detection, the system can be applied, for example, to safety alarms and environmental control systems, such as exhaust level detectors, and the sensing device should be selected in a corresponding manner.

Similarly, the nature of the alarm inducing condition, as mentioned above, will vary with the application of the system.

In connection with a fire detection system, the sensing means may comprise a heat detector, which is activatable depending on the detection of a predetermined temperature level. Thus can

7506723-1 ₆ the sensing means comprise a change rate detector type detector or a fixed temperature detector type detector. Alternatively or as further examples, the sensing element may comprise or consist of a smoke level detector, which may operate in dependence on a predetermined smoke density level.

The system has special application in fire alarm systems in multi-storey buildings. In this case, a plurality of detector heads can be strategically placed at specific locations on each floor of the building for transmitting signals to one or more receivers, which can be located on each floor. The receivers at the different floors would then be connected via a Transmission line to a single control unit, W which could be arranged to give an audible and / or visible indication of the operating condition.

Some circuits, which are not unique to any receiver and which: ig.5 are common to all receivers belonging to any control unit, could be included in a single module in connection with the control unit.

. Each transmitter should normally be arranged to transmit a uniquely coded signal. Such a signal can be obtained by amplitude, frequency or phase modulation of a carrier signal. The invention is described in more detail below with reference to the accompanying drawings, in which Fig. 1 schematically shows a multi-storey building comprising a fire detection system, fig. 2 Fig. 3 shows a block diagram of a transmitter operating with a single sensing means and an associated receiver located at a distance therefrom, which forms part of the system, Fig. 3 shows a block diagram of a transmitter in accordance with Fig. 2, but more in detail, Figs. 4, 5 and 6A-6B (Fig. 6b is a continuation of Fig. 6A) show block diagrams of the receiver of Fig. 2 in more detail, and Figs. 7 and 8 show logical signals and signal-time relations which are relevant to the function of the receiver.

As shown in Fig. 1, a plurality of thermal sensing means transmitting units 20 are mounted in the ceiling 21 on each floor of a multi-storey building 22. The sensing means, which may have a standard construction and which are largely of secondary importance to the invention, operate in a known manner to detect any increase in ambient temperature level, which increase is large enough to indicate the presence of a local fire. Once they have detected the presence of a local fire condition, the sensing means activates a switching device present in the unit, and this in turn causes an associated transmitter to transmit signals in a

7506723-1 larnmod. The activation of the transmitter and the transmission process will be described in the following.

At least one receiver 23 is located on each floor of the building 22 to detect each signal transmitted by an associated transmitter, and the receivers are connected by a cable 24 to a single control unit 25, which should normally contain an indicator panel. The cable 24 should usually be arranged in the building's main cable installation between the floors. .

The control unit 25 comprises a local alarm and fault indication system 10, and it can be connected by means of a transmission line 26 to an external alarm in a nearby fire station or other fire monitoring station.

The function of the receivers 23 will be explained in more detail later in the description.

Each unit 20, which comprises a sensing means and a transmitter, should normally comprise two interconnected housings (not shown), one of which comprises the sensing means 35 (which can simply be considered as a heat-actuated switch) and of which it others include the transmitter 27. The transmitter 20 housing also includes a dry cell type battery 30 for powering the transmitter and for providing switching current to the sensing means. No wire connections have been made to the sensing transmitter units 20 from any external power supply source.

Fig. 2 shows (schematically) the interaction between a sensor-transmitter unit 20 and an associated receiver 23. Fig. 2 also shows the primary components in both transmitter and receiver.

Each transmitter 27 or, alternatively, each of a number of groups of transmitters is arranged to transmit uniquely coded signals in order that a response can be generated only at an associated receiver. The signals are obtained by digital (time division multiplex) modulation of a radio frequency carrier signal in the manner which will be described below.

Under normal operating conditions (ie when the transmitter 27 transmits signals in a monitoring mode and the sensing device has not been activated), each transmitter transmits coded pulse trains with the frequency. then one pulse train, each pulse train having a duration of 600. These monitoring mode signals are shown schematically in Fig. 2, the RF carrier component of the signals having been omitted for the purpose of providing a clearer representation.

7506723-1

When operating in the alarm mode (ie when activating the sensing means), the transmitter 27 transmits coded pulse trains with a higher repetition frequency. Thus, in the alarm mode, a series of 20 pulse trains is transmitted where each pulse train has a duration of 600 .mu.s (as in the monitoring mode), and the pulse trains appear at a time interval of 200 .mu.s. The coding used in relation to the signals transmitted in the alarm mode of the respective transmitters is the same as the coding used in relation to the monitoring mode signals. The only difference between the signals transmitted in each mode is in the signal repetition frequency.

During fault conditions, which can occur in the event of a fault in the battery or on any component, no signals were transmitted by the transmitter 27.

The receiver 23 functions, as shown in Fig. 2, to detect signals transmitted by an associated transmitter 27 and to also detect any mode change of the transmitter transmission. At the same time, the receiver also detects the absence of each signal transmission from an associated transmitter, and if no signal detection is made within a prescribed period of 10 minutes, a false alarm will be obtained.

A more detailed description of the function of the transmitter and receiver 20 will now be given with reference to Fig. 2.

The transmitter 27 comprises a battery 30, which provides power for a signal generator and signal processing unit 31 and additional components in the transmitter. The signal generator and the signal processing unit 31 generate a modulating signal, which is coded in order to identify a particular transmitter. When the transmitter is operating in monitoring mode, monitoring includes ..... the signal is a series of pulse trains, each of which has a duration of 600 / ice, and where successive pulse trains have a time interval of ..... 1 minute. The modulating signal is used to modulate an RF signal carrier signal in a signal direction subsequent carrier signal generator modulator 32, and the composite signal is amplified in the power amplifier 33 and transmitted by an antenna 3

The battery 30 also supplies current to the sensing means 35, which, when activated to a local fire condition, causes a voltage change at the signal generator and the signal processing unit 31. This then initiates a change in the operation of the signal processing unit, thereby generating a modulating signal, which includes a series of pulse trains, each of which has the same duration as those generated in the monitoring mode, but where the successive pulse trains occur at a time interval of only 200 > us.

s

7506723-1

Each output signal from the transmitter 27 is received by means of the antenna 36 on the receiver 23 and is processed in the RF and MF stages 37 and 38 in the receiver. These steps are structured in the usual way.

Thereafter, the output signal from the transmitter is demodulated in a demodulator 39, and the signal is evaluated in what is called a signal evaluation step * 0. In the evaluation step, the received signal is checked for interference, for the presence of noise and for acceptable coding.

The signal that has been evaluated is analyzed in a mode detector 41, which in fact forms part of the signal evaluation step and which detects the transmission mode. The mode detector operates so as to provide an output signal under any of the following conditions: i) if at least one (evaluated) pulse train with a duration of 600 is received and detected within 1-10 minutes after a previous · ξ15 (also evaluated) pulse train, then the mode detector 41 will provide an output signal to indicate that the system is operating properly in the monitoring mode. The indication is given by means of a monitoring indicator 42.

ii) If at least one (evaluated) pulse train of 600 yus is received and detected within 200 yus - 16 as after a previous pulse train, then the mode detector will provide an output signal to indicate that the system is operating in alarm mode. This indication is given by means of an alarm indicator 43.

iii) If no evaluated pulse train is received within a period of 10 minutes after receiving a previous (evaluated) pulse train, then the mode detector 41 will provide an output signal to indicate a fault condition in the system. This indication is given by means of an error indicator 44.

Transmitter 27 should normally operate in the monitoring mode, so it should be easy to determine if the receiver is responding to a change in the transmission from the monitoring mode to the alarm mode, or if no signal transmission is detected within each period of successive 10 minute periods. .

The design of the transmitter and receiver is shown schematically only in Fig. 2 in order to obtain a simplified description of how the system works in general. A more detailed description of the system is now given below with reference to Figs. 3-8. '

The transmitter 27 comprises, as shown in Fig. 3, the battery 30, which provides power supply through a manually operated isolation switch * 5 for a timer 46 for 1 minute, for a cup *

7506723-1 ₁₀ device 47, which in turn provides power to the entire circuit device forming the signal generator and signal processing unit 31 and to the RF oscillator modulator J2, to a further switching device 48 which provides power to the RF power amplifier 33, and to the sensing means 35. which is preferably a normally closed thermal switch). Power through the sensing means is supplied as a gate control signal to a gate type logic circuit 58. ·

The 1 minute timer 46 generates a trigger pulse which turns on the switch device 47. It also activates a monostable flip-flop 49 (for delay), which provides a lock-in period with a duration sufficient to allow stabilization of the RF oscillator 32 and to allow that a 24-bit code is shifted into a shift register 50 from a code link device 60. During the same latch 015 period, dividers 51-55 and 61 are reset, a two-phase generator 56 is also reset and reset, and a clock signal source 57 with the frequency 80 kHz is prevented from transmitting clock signals.

The (delay) flip-flop 49 also supplies a blocking signal to the logic circuit 58, which uses the signal to prevent the transmission of an output signal from the two-phase generator 56 to the RF oscillator 32 via a gate 59.

At the end of the blocking period, the clock signal source 57 starts transmitting clock signals, and the blocking signal to the logic circuit · 58 is canceled. The logic circuit 58 then switches on the switch device 48, 25 which then provides power supply to the RF power amplifier 33> and cancels the blocking signal to the gate 59. Thus signal transmission is then obtained between the two-phase generator 56 and the RF oscillator 32.

An output signal (rectangular wave) from the clock signal source 57 is fed to the divider network 51-53. The output signal from the divider 51 is a clock signal with the frequency 40 kHz and is fed via the logic circuit 58 to the shift register 50, which is caused to output a base code signal in step with the obtained clock signals. The base code signal is output from the code link device 60, which generates the code logic pattern which^T is shifted into the shift register 50.

The logic pattern includes a series of logic ⁿ0ⁿ and “1% generated to represent a selected 24-bit code.

The base code from the shift register 50 is used to modulate another output signal (rectangular wave) of 80 kHz, which is fed from the clock signal source 57 to the two-phase generator 56. The modulated output signal from the two-phase generator * 56 comprises a signal with a pulse frequency which

7506723-1 is equal to the bit rate of the modulating signal each time a bit in the base code is logical 1 and equal to twice the bit rate each time a bit in the base code is logical 0.

The output of the two-phase generator is fed via gate 59 to the RF oscillator 32, where it is used to frequency modulate an RF carrier signal having a carrier frequency of 450 MHz. This modulated signal is then amplified in the amplifier 33 and transmitted by the antenna 34.

The output signal from the dividers 52 and 53, when combined in the logic circuit 58, generates trigger-off signals, which serve to disconnect the switch devices 47 and 48. This causes the power supply to the signal generator and the signal processing unit 31 except from the timer 46 and the switches 4γ and 48. and to the RF oscillator 32 and to the RF amplifier 33 are removed. This stops the signal transmission after transmission of a pulse train, which is formed by the 24-bit code.

In monitoring mode, this cycle is repeated once every 60 seconds. Re-initiation of the cycle is controlled by the timer 46 for one minute. If a signal is transmitted in the monitoring mode and an alarm condition occurs, then the normally closed sensing switch 35 (which normally provides the gate control signal to the logic circuit 58) breaks and causes a state change of the control signal. This in turn blocks (the above-mentioned) trigger-off signals, which would otherwise cause a break of the switch devices 47 and 48. This blocking of the trigger-off signal allows the dividers 51-53 to continue counting and to continue to give an output signal to the logic circuit 58. The logic circuit 58 then functions to transmit the 40 kHz clock signal at time intervals to block the shift register 50 from outputting the base code signal in step with the clock signals for a period of 200 seconds following the transmission of each pulse train. In addition, an output signal from the divider 61 is supplied to the logic circuit 58 at intervals of 16 ms, and this in turn causes the switches 47 and 48 to be broken then. Thus, the signal transmission in the alarm mode is limited to the transmission of 20 pulse trains over a total period of 16 ms, where each pulse train has a duration of 600 .mu.s, and where the pulse trains have a time interval of 200 .mu.s.

To prevent the transmitter from resuming operation in the monitoring mode after it has transmitted an alarm mode signal, a blocking signal is supplied to the timer 46 for one minute.

7506723-1

If a signal is not transmitted in the monitoring mode and an alarm condition occurs (ie during the one-minute period between successive monitoring mode transmissions), the normally closed switch, which constitutes the sensor means 35, breaks. This again serves to block the trigger-off signals which would otherwise break the switch devices 47 and 48 during transmission of the alarm signal.

Because the switches 4? and 48 would be disconnected "at the time when alarm condition is sensed, activation of the sensing means 35 also results in a trigger pulse being supplied to the switch 47 via a capacitor 62. A trigger pulse is also supplied to the monostable flip-flop 4g. This then initiates the transmitter to operate just as if a monitoring mode transmission were to occur, but the cycle is repeated in the manner described above in connection with the alarm mode function.

It has been mentioned at this stage that the 24-bit code transmitted by the transmitter (such as a series of two-phase "1" and "0" printed on the carrier) serves a number of functions. The order (ie the coding) between the bits is determined by the code link device in each transmitter in order to identify the location of or the address of the respective transmissions. Three of the bits were used to identify the building in which the transmitter is located, four were used to identify the floor of the building and six bits were used to locate the transmitter within that floor. Of the remaining eleven bits, four are used to establish proper operation of the receiver's station selector device and the receiver's logic (which has been mentioned above), one bit being a start bit, one being a parity bit, one a bit representing the end of the code, and the the remaining four bits are spare bits.

The logic circuits of a receiver located on one of the floors of the building may need to process a very large number of transmissions from the transmitters located on its own floor and from transmitters on other floors within the same building and * from nearby buildings. Therefore, the logic circuits of the receiver must reject all signals except transmissions, which originate from associated transmitters, which are located on the same floor of the same building as the receiver. '

The manner in which this is achieved will be apparent from the following description of the function of the receiver, which is given with reference to Figs. 4-8. One. part of the receiver components 40 shown in Fig. 4 have already been indicated in connection with Fig. 2 and the same reference

7506723-1 drawings were used for these.

In the signal direction after the receiver's antenna 36 there is a bandpass filter 65, which serves to reduce existing noise in a received signal. The received signal is then amplified in a subsequent two-stage, wideband RF amplifier / filter / mixer 320, where it (in the last stage) is superimposed with the signal from a local oscillator in order to provide an MF signal.

The MF signal is amplified in the MF amplifier 3θ (with fixed gain), and an output signal from the MF amplifier is further amplified in a select amplifier 66, which does not provide an output signal unless the input signal has a predetermined character, to provide a selected signal D. The second output signal from the MF amplifier 38 passes through a two-stage bandpass limiter 67, which together with a subsequent MF switch 68 and a discriminator 69 form part of the demodulator 39. The MF switch 68 operates to mute the system between received transmissions or reception of the selected signal D from the selection amplifier 66.

The output signal from the MF switch is fed to the discriminator 69, where the received signal is demodulated to output the (transmitter generating 20 de) encoded two-phase signal. Since this signal will contain unwanted frequencies, it is processed in a signal direction subsequent filter 70 and then fed through a compensation amplifier 71. '

The output signal from the compensation amplifier 71 is fed to a switching comparator 72, which provides a signal A via the gate 114. The output signal 114 is also controlled by the signal D from the selector amplifier 66, which means that the output signal A is only received by a signal at the antenna 36. The output signal A is thus representative of the ..... transmitted, encoded two-phase signal. * '-30. It should be mentioned here that fig. 7 shows the relationship between the logic signals A, B, W, CP, Z, V, FZP, H, FSTR, G and D, which will be stated in the description (or have already been). Fig. 8 shows the relationship between the timing signals G, JJ, K, WW, Q, RR, N, XX,^Ύ SADSTR, YY, X, ABORT, ZZ and ATERST, which will also be described in more detail below. Some other signals - namely ZF, CLF, NIF, PAROK, BIT 1-6, S, R, REJ, ACC, ONSIG, DD, M, TT, TX, CL, CUFRS,. ZFIRE, ZP, J, I and L - are also indicated in the description and are shown in Figs. 5 and / or 6 but are not specifically shown in Figs. 7 or 8.

The first three bits of the 24-bit code are "liar" and modulate the transmitter's carrier frequency over a period of approximately 75 Ms.

7506723-1 i¹*

During this period, the station station selector of the receiver (formed by the units 37, 38 and 39) detects this signal as an acceptable signal, which causes the selector amplifier 66 to leave the signal D.

The signal A is fed to signal converter 73, which generates an output signal B, which is formed by positive pulses of 200 ns, which have either a pulse gap of 12.5 or 25 /¹³ and representing transmissions of the encoded two-phase signal A.

The coded two-phase signal A comprises a signal with a pulse length which is equal to the bit frequency of the modulating signal n (when the base code is a logic^M 1, and equal to the double bit rate period (12, 5 / is), when the base code is a logical ¹¹ 0, whereby it thus = produces transitions with periods of 25 and 12.5 /¹³ .

The logic is so constructed that it accepts signals that have timing errors of up to 20 ?. The logic will therefore accept transmissions, which have a space of 10-15 / *³, which is 12.5 /¹⁵ + 20 ί, or those who come with a space of 20-30 / * s, which is 25 /¹³ + 20

The logic circuit associated with the signal evaluation is constructed in such a way that the signals which come at a space which is smaller than, say, 8 / is will cause the signal to be rejected by means of a zero error circuit formed by a monostable rocker 111 and a gate 83. Those who appear at intervals of more than let's say 33 /^as will cause rejection of the signal by means of the clock signal length error circuit formed by a mo25 nostable flip-flop 84 and the gate 90.

When the signal B consists of two pulses which are separated by a time period which is greater than 17.5 / ice, a monostable flip-flop 74 is brought down to a pulse length of 17.5 / ice to generate a trigger signal C, which via the gate 76 generates the signal Z, which causes the data type flip-flop ^ 75 to be reset.

The data-type bistable flip-flop 75 has already been reset because a reset signal has been received as a result of other logic signaling the end of the processing of an earlier signal, which will be described later.

When the signal B consists of two pulses separated by a period shorter than 17.5 .mu.s, the monostable flip-flop 74 is still running until 17.5 .mu.s has been applied, whereby a signal W is generated which allows gate 91 to provide an output signal FZP, which is used to set the data type flip-flop 75. This in turn gives a decoded base code output H. and a

7506723-1 second output ZP. The output signal ZP is used to set a bistable flip-flop 77, which remains set and provides an output signal FSTR, which is used to activate the gate 79 until the flip-flop 77 is reset by the reset signal, in the manner which will be described in more detail below.

For the purpose of generating clock signal information G, a monostable flip-flop 73 with the pulse length 1 .yis is triggered by the trailing edge of the output signal W from flip-flop Ib for every 25 eus, and gives a clock pulse CP. The signal G is thus the signal CP provided that the two blocking signals PSTR 10 from the flip-flop 77 and J from a bistable flip-flop 80 for the end of a strobe pulse are obtained. Thus, in this way, a first s 0 is detected and, as will be described in more detail, a previous sensing signal has been processed, completely filled a shift register 81 and sets the bistable flip-flop 80 to end on strobe pulse via the signal I.

To ensure that biphasic zeros are not accepted if they are formed by pulses which are separated by a time period of less than δ ^ με, a monostable flip-flop 111 having a period length of 8, us provides a blocking signal to gate 91. If thus a blocking time of 20 3 / Us is initiated by the trailing edge of each pulse Z and a second pulse in the signal B occurs within 8 after the previous pulse in the signal B, then the flip-flop 111 functions so as to block the gate 91 via the signal V.

A second output signal L from the monostable flip-flop 111 is used to generate a zero error signal ZF via gate 83. However, the output signal ZF is blocked by the output signal K from a monostable flip-flop 82 with a period time of 45 μs, which flip-flop will to be described further below.

Accordingly, the output signal ZF is blocked if the gate signals B and G of the gate 76 do not indicate the presence of pulses at intervals which are less than 8_zus.

The output signals B are consequently fed to a monostable flip-flop 84 with a period length of 33 μs in order to perform a further f test of the period between the pulses. If the period between the pulses 35 is greater than 33 / is, the flip-flop 84 will generate a clock error signal CLF, provided that a gate 90 is not blocked by the output signal,. FSTR from the bistable flip-flop 77 for the first zero or by an output signal JJ from the flip-flop 80 for the end of the strobe pulse. This means that measurements are only made on the incoming signal after a first 0 has been detected and until

7506723-1 _1β that the shift register 81 has been filled in completely.

The output signal JJ is also used to trigger the flip-flop 82, the output signal K of which is used to block the gate 8j (as mentioned above) to ensure that during the masking period of 45 μs erroneous 0: cm, a false signal ZF is generated. The false 0s can be generated in the receiver's station selector, if the signal selection were slower than the case with the carrier frequency of the sensor means, resulting in noise deviations, resulting in false pulses at B, the period intervals of this signal being less than 8.

Thereafter, the output signal K from the monostable flip-flop 82 with a period length of 45 μs resets the bistable interference flip-flop 85, the trailing edge of this signal of 45 triggers a monostable flip-flop 86 with a period length of 100 μs, the output signal WW of which activates a gate 113, output signal sets the interference flip-flop 85 (due to pulse signals at B) at any time during this period of 100 .mu.s. This indicates an interference condition that is causing it. an output signal NIF.

The trailing edge of the output signal WW with the pulse length 100 _zus initiates 20 monη monostable flip-flop 104 with the period length a ^ us, which provides a delay period or setting time of a ^ s. This delay period is needed to allow signals from the circuit to accept or reject (which will be described later) to be stabilized, before being sampled at the inputs of gates 106 and 116, which gates will also be described later. The trailing edge of this delay period causes the rocker to generate a pulse Q. a duration of one ^ gs, the use of which will also be described in more detail below.

The clock pulses G are used to clock control the base code signal H ^ 30 into the shift register 81. After 20 clock pulses, the first clocked bit (ie the first bit after the zero bit) moves to the 20th bit position. The remaining 19 bits of the transmitter signal are also clocked into their respective bit positions. When the 20th bit position is filled, the output of the 20th bistable stage 35 changes in the state of the shift register and gives an output signal I, which is used to give signal to the bistable flip-flop 80 to end the strobe pulse and further prevents the output of pulses G from the gate 79When the signal G clock controls the shift register 81, a bistable parity flip-flop 95 counts ^w 1 'bits, as they pass. * After all 40 bits have been clocked and the count is odd, ₁₇ 7506723-1 man to have an output signal PAROK on the output of the parity flip-flop 95. If the count is even, there is no output signal PAROK, which consequently means that the pulse train is rejected via an acceptance / rejection / gate 97, which will be described below.

Building and floor code signals R and S are monitored by the gate in cooperation with a code link device 99. In order to obtain an acceptance signal BFOK from the gate 96, it is required that the input signals S and R and also the input signal NIF are such that ¹¹ 1s are generated at the gate's 96 respective inputs. If the input codes S and R are acce10 tabla, the lines in the code are transmitted directly to the inputs 96 of the gate, and the 0s are transmitted to the inputs of the gate 96 via an inverter 100. This special receiver is coded to receive only those signals which belong to it floor of the building, to which the recipient is destined.

igj.5 When the six-bit signals generate the bit signal BIT 1-6 placed in the shift register, the parity output signal PAROK, the selector input signal D and the building, floor and noise acceptance signal BFOK are tested by gate 97 in order to generate an acceptance or rejection signal ACC and FÖRK, respectively. ·

The sample signal D should remain at a high level below 40-50 jus after the end of the transition to allow testing to be performed for interference. The selection signal D is also supplied to a monostable flip-flop 98 with a period length of one ^ s, which flip-flop generates a trigger pulse ON SIG, which in turn can cause the gate 101 to trigger a general reset, if the selection is not within a period of 8 '850 / is produced by a monostable rocker 92 with a period length of

850 / is. The ONSIG signal thus indicates the start of a new sensing transmission, as determined by the selection signal D.

..... A comparison register 93 comprising six ratchet gates, whose inputs M contain the sensor address code, will, when a pulse N is applied to one (the generation of which will be described later) to the gate input of the gates, cause the input signals M to appear at the outputs DD. The contents of the comparison register 93 come^r always be the transmitter address code received from a previous sensor transmission and stored until it receives a new trigger pulse N.

A comparator 94 performs a bit-by-bit comparison between new and previous sensor addresses by continuously comparing the input signals M with the output signals DD. If each bit in the new address 40 is the same as the corresponding bit in the old address, the output

7506723-1 ₁₈ a Z FIRE at a high level. However, the Z BRAND output is disregarded until gate 95 is activated.

If the sensor signal is accepted, transmitted pulses RR (which is the timing pulse Q) at the output of gate 106 are fed to gate 95. During the interval of pulse RR, the signal Z BRAND is tested at gate 95 · If a fire condition is not signaled, the output 'Z BRAND is at a low level and regardless of the output of flip-flop 107, which is a monostable flip-flop with a period length of 16 ms, no pulse will occur at the output of gate 95.

If there is a fire condition (when the output Z FIRE is at a high level), then one of two things will happen. If the period on vip ££ pan 107 has not elapsed, ie it has not been triggered by N, then no pulse will appear on the output 95 of the gate. If the pulse from the flip-flop 107 has been applied, a CUFRS signal is generated, which causes a bistable flip-flop 319 to occur to be set on fire.

When the flip-flop 107 is triggered by the signal N, it represents an accepted transmission from a transmitter. The purpose of flip-flop 107 is to create discrimination between a true fire condition and a possible false “fire condition”. In a "real" fire sensing transmission, the 2-bit pulse train is repeated 20 times at an interval of 200 μs between the pulse trains, and a fire burst signal has a duration of 16 ms, as mentioned earlier. If two consecutive transmissions from the same sensing means are received within 16 ms, without the receiver detecting acceptable transitions from a second transmitter (and thus a different transmitter address between them, the first transmitter is judged to transmit a fire signal. If the above condition occurs but with time, which is longer than 16 ms, no fire condition is detected.

It is possible for two consecutive transmissions of the type surveillance mode transmission to emanate from the same transmitter, but these should have a distance of about one minute.

If the reception of a fire signal does not interfere with any other signal, the detection of a fire should be able to be completed after the processing of the second pulse train of the 20 pulse trains. If the interference occurs at the first pulse train (ie this is not accepted due to one or more of the signal tests), one relies on the second and third pulse trains to reach fire detection. Similarly, if interference causes rejection of the first pulse trains, the first two free pulse trains result in a fire detection. If interference is received from another transmitter, which signals overlap one or two of the fire pulses, then all overlapping transmissions will be rejected. The extinction of the fire will then be achieved by two separate free fire pulse trains (eg pulse trains 1 and 4, if the second and third of the pulse trains overlap). If the fire signal transmission overlaps with a series of other sensing transmissions, the difference can extend up to 18 fire pulse trains (ie 14.4 ms) as the worst case, when * the first and last pulse trains in the fire signal will still result in a fire detection. .

σ The gate pulse RR is fed in addition to the gate 95 to a monosta10 car flip-flop 105, where the trailing edge of the pulse RR triggers the flip-flop 105, which generates the timing pulse N. These timing pulses N allow, as mentioned above, the inputs on the inputs M This is known as a strobe activity. At the same time, the signal N triggers the monostable flip-flop 107 with an activation time of 16 ms, which is thus triggered by each accepted transmission.

The trailing edge of the signal N is used to trigger the monostable flip-flop 108 and this in turn serves to generate a transmitter address signal SADSTR. This pulse is used to activate a transmitter 20 address decoder 117 to decode signals DD, which are stored in the six-bit comparison register 93, and which signals represent the address of the transmitter which has just transmitted. An address output signal is provided, which is supplied to its respective error processing circuits within the dashed lines 117-157, of which only three are shown (Fig. 6b), and also to the inputs of the fire processing circuits 158-198, of which only three are shown in Fig. 6b. '

The operation of a typical fault and fire treatment circuit will be described below.

The trailing edge of the signal SADSTR is used to trigger the mono ^ stable flip-flop 109> and this serves to generate a delay on a_zwhich delay is required to ensure that the trailing edge of the pulse SADSTR does not coincide with the start of the general reset pulse X. The trailing edge of a delay signal * YY on one is used to trigger a monostable flip-flop 110, which serves to generate the general the reset pulse X, which is fed to a monostable reset flip-flop 115 and to the gate. 101.

The normal signal processing function of the general reset circuits including the flip-flop 92, the flip-flops 102 and 115 'HO and the gate 101 is as follows.

7506723-1

The monostable flip-flop 92 with a setting time of 850 jas to indicate excess time is triggered by positioning the bistable flip-flop 102 to detect the first "0; an"^M_vin the signal FXP, which is fed by the gate 91. The output signal from the flip-flop 92, ZZ, causes the reset flip-flop 115 to be reset because either an input signal CL is present before the period of 850 microns has expired or by the natural the expiration of the period of 850 _?us.

The free or true input signal CL can be forced to a low level by any of the following fire test pulses appearing at the input of gate 101: Z ERROR, CLF, ONSIG, ABORTION or X.

The ABORT signal is generated at the output of gate 116, if a rejection signal FÖRK is present at the output of gate 97. The gate 116 is thus activated by the signal FÖRK and therefore allows the pulse Q to become the signal ABORT._z The end of the output signal from the flip-flop 92 by the pulse signal on

850 is naturally required to protect against the possibility of a transmission, which ends in the middle of the pulse train (due to a noise burst signal, etc.) which leaves the shift register partially filled, and the circuits are not prepared for a subsequent transmission.

In general, if any of the above five test pulses the natural expiration will ensure the reset of the signal processing circuits.

The operation of one of the fault handling circuits 117-157 (eg 117) and one of the fire treatment circuits 158-198 (eg 158), which have been indicated above, will now be described.

The bistable flip-flop 190 for detecting that the sensing units function satisfactorily is reset at the beginning of a cycle of 10 minutes by a signal TX from a bistable flip-flop 191 with a set time of 10 minutes. The flip-flop 190 is thus set to wait for reception of transmission indicating that the transmitter is in operation from the sensor address decoder 117. During the following interval of 10 minutes, several monitoring transmissions (up to 10 within 10 minutes) are expected. When a transmission is received, the bistable flip-flop 190 will store this fact by changing its output to a set state.

At the end of the cycle of 10 minutes, the bistable flip-flop 192 is triggered for errors on the sensor / transmitter unit with an output signal TT from the flip-flop 191>, which causes the output signal from the flip-flop 190 to be tested.

IF the flip-flop 190 has been set, which indicates that the sensor / transmitter unit is in operation, the output signal of the detector flip-flop 192 does not change

7506723-1 condition, and consequently no further action occurs · If the output of the flip-flop 190 is not set (ie the flip-flop remains reset), which indicates that no function transfer has been received during the last. 10 min, the test gives an error indication. This causes the sensor fault flip-flop 192 to be set, and a fault lamp 193 will be lit.

The sensor error flip-flop 192 and the lamp 193 remain in this state until they are manually reset by means of an error reset button 194.

The timer 191 with the set time 10 min is also reset 10 by the action of the closing of the error reset button 194.

The operating cycle of the timer 191 is thus that pulses TT and TX are generated continuously at intervals of 10 minutes.

The bistable flip-flop 319, which indicates the presence of fire, when set by a trigger pulse CURFS, generates an input signal to _r.: - yl5 all gates 195-235, which belong to all fire treatment circuits 158-198. At the same time, the sensor address decoder 117 provides an output signal to a special address belonging to the fire treatment circuits 158-198, which output signal activates an associated gate, e.g. gate 195, so that it generates an output signal GG, which sets the flip-flop 20 236. When the flip-flop 236 is set, an associated fire lamp 227 will light up and remain lit until a manual fire reset button 318 is pressed, whereupon the flip-flop 236 is reset and the lamp goes out. ,

The flip-flop 319 for detecting the occurrence of a fire is used to store a fire condition for a just long enough time to set one of the bistable flip-flops 236-276 for indicating fire at one of the sensor / transmitter units and to allow the sensor code to be decoded in order to determine which detector has sensed the fire. . >

• ^ 0 At the end of the treatment of the fire pulse train, the rocker is reset

319 of the signal processing reset switch 115, so that it is ready to receive a fire detection from another associated transmitter.

7506723-1 ₂₂