Cordless telephone

(42) Date of commencement of the patent: 15. 3.1997 (45) Date of issue: 25.11.1997

<td>(30) Priority:</td><td>(73) Patent owner:</td><td></td>

<td>23. 3.1988 JP 68725/1988 claimed.</td><td>SONY CORPORATION TOKYO (JP).</td><td></td>

<td>(56) Documents:</td><td></td><td></td>

<td>EP 0176855A EP 0227185A EP 0185972A</td><td></td><td></td>

(54) CORDLESS TELEPHONE (57) A cordless telephone contains a basic unit connected to the telephone network line and a handset unit with a rechargeable battery as the operating voltage source. The hand unit and the base unit are connected during a telephone conversation above a radio channel. Before a telephone call, one of the two units sends an identification code to the other unit. The identification code issued by one unit is tested in the other unit and a transmission channel is activated when the code is determined to be correct. The hand unit includes a first charging detecting circuit which detects a charging of the battery, and a first memory for storing the identification code, whereas the basic unit includes a charging circuit for charging the battery, a second charging detecting circuit for detecting the charging of the CQ battery by the charging circuit, and a second storage for storing the Idantifikationskodes. When the first charging detection circuit detects a charging of the battery, the identification code stored in the second memory is read out via charging contacts on the base and the hand unit and stored in the first memory.

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The invention relates to a cordless telephone according to the preamble of claim 1.

Such cordless telephone systems have been proposed and put into practice in Japan, the US and other countries.

Such a system will be described with reference to FIGS. 1 to 6, for example. Showing:

1 is a perspective view showing the operation of a hand unit and a basic unit:

FIG. 2 is a block diagram of the overall circuit of a hand unit of a conventional cordless telephone; FIG.

FIG. 3 is a block diagram of the overall circuit of a basic unit of a conventional cordless telephone; FIG.

FIG. 4 is a diagram showing a signal format usable for transmission; FIG.

FIGS. 5A and 5B are a flow chart showing the sequence of operations performed by a conventional hand-held unit and basic unit;

Fig. 6 is a perspective view of an apparatus showing a state where the hand unit is set on the base unit to charge the battery;

As Fig. 1 shows, a cordless telephone includes a transmitter / receiver unit formed by a handset 1 and a transmitter / receiver unit formed by a base unit 2. The basic unit 2 is connected to a line 3 of a telephone network. The basic unit 2 and the handset 1 communicate with each other via radio waves. Accordingly, a telephone subscriber with a cordless telephone can make calls or receive incoming calls via the handset 1 as well as a conventional telephone.

The described cordless telephone has a functional area - ie the distance in which the hand unit 1 can be spaced from the base unit 2 during telephone conversations - from about 300 m. The frequency of the radio waves transmitted between the hand unit 1 and the base unit 2 is in the 49 MHz band for the upper channel (ie in a transmission from the hand unit 1 to the base unit 2) and in the 46 MHz band in the lower channel (ie in a transmission from the base unit 2 to the hand unit 1), and in the US ten duplex channels are enabled for each system.

The subscriber can take the hand unit 1 everywhere, for example, outside the home while making or receiving phone calls. The cordless phone also has not a conventional phone adhering disadvantage of the telephone cord, which can be twisted and obstructed.

However, since the signal transmission between the hand unit 1 and the base unit 2 takes place via radio waves, the call of a subscriber can be tapped at a via his own handset 1 and the base unit 2 in a telephone call by an unauthorized third party who also uses a cordless telephone.

To avoid this problem, a common identification code (ID code) is provided for the hand unit 1 and the basic unit 2. A hand unit 1 and a basic unit 2 intended for use with each other are provided with the same identification code selected from, for example, binary code values ​​represented by 20 bits.

In establishing a connection between the hand unit 1 and the base unit 2, the ID code is sent from one unit to another, and the unit receiving the transmission determines whether or not the received ID code corresponds to the ID code previously stored therein. If the sent and previously stored ID code are identical, a conversation channel is activated and the participant is connected to a called or calling party.

Fig. 2 shows a block diagram of the overall arrangement of a typical handset unit 1 of the cordless telephone using the ID code described above. The hand unit 1 includes a transmission circuit 110 and a reception circuit 120.

FIG. 3 shows a block diagram of the overall arrangement of a typical basic unit 2 which includes a transmission circuit 210 and a reception circuit 220.

In the process of making an outgoing call, the audio signal St from a microphone 111 through signal processing circuits including a low frequency amplifier 112, a low pass filter 113 and an adder 114 in this order is applied to a phase locked loop voltage controlled oscillator or VCO (not shown) ) 115 in which the signal St is converted into a frequency-modulated (FM) signal Su for the upper channel. The FM signal Su is applied to an antenna 100 via signal processing circuits which comprise a bandpass filter 116 whose passband passes through all the upper channels, a high frequency power amplifier 117 and a duplexer 118 in that order, through which the FM signal Su to the fundamental unit 2 is sent.

As shown in FIG. 3, the signal (the radio wave) Su radiated from the hand unit 1 is received at the fundamental unit 2 from an antenna 200 and signal processing circuits including a duplexer 218, a high frequency amplifier 221 and a band pass filter 222 whose pass band is all

AT 403 104 B upper channels passes, contained in this order, fed to a mixer 223. The mixer 223 is further supplied with a predetermined frequency local oscillation signal from a PLL circuit 224, whereupon the signal Su is converted into an intermediate frequency signal. This intermediate frequency signal is applied via an intermediate frequency amplifier 225 to an FM demodulator circuit 226 and there demodulated to the audio signal St. The audio signal St is then output to a telephone line 3 via signal processing circuits which supply a low-frequency amplifier 227, a two-line / four-line converter 231 and a relay contact 232.

Upon receipt of an incoming call from the telephone line 3, the audio signal Sr is processed by the telephone line 3 in a similar manner and delivered to a receiving circuit 120 of the hand unit 1. More specifically, the audio signal Sr is supplied from the telephone line 3 to a VCO (not shown) of a PLL circuit 215 through signal processing circuits including the relay contact 232, the converter 231, a low frequency amplifier 212, a low pass filter 213 and the adder 214 in this order in which the signal Sr is converted to an FM signal Sd in the lower channel forming a pair with the FM signal Su in the upper channel. The signal Sd is applied to the antenna 200 via a band-pass filter 216 whose passband passes all lower channels, a high-frequency power amplifier 217, and the duplexer 218 in this order, through which the signal Sd is output to the hand-held unit 1.

As shown in FIG. 2 it can be seen that the signal Sd is received by the base unit 2 from the antenna 100 of the hand-held unit 1 and supplied to a mixer 123 in this order via the duplexer 118, a high-frequency amplifier 121 and a band-pass filter 11 whose passband passes all lower channels. The mixer 123 also receives a local oscillation signal of predetermined frequency from a PLL circuit 124, so that the signal Sd is converted into an intermediate frequency signal. This intermediate frequency signal is applied via an intermediate frequency amplifier 125 to an FM demodulator 126 and demodulated from this to the audio signal Sr, which is then delivered via a low-frequency amplifier 127 to the speaker 128.

The handset unit 1 includes a control circuit 140 for controlling the transmission channels, etc. The control circuit is composed of a one-chip microcomputer having a central processing unit (CPU) 141 adapted for, for example, 4-bit parallel processing, a read-only memory (ROM) 142 containing control programs for controlling the operation of the CPU, a memory random access memory (RAM) 143 for use as a desktop, an input port 144, and an output port 145. The ROM 142 also includes a program 300 which is represented by the flowchart in FIG. 5 is shown.

The microcomputer 140 is connected to a keyboard 141, a talk key 152 and a mode key 153. The keyboard 151 includes non-latching pushbuttons for entering a desired telephone number. It contains ten keys, each representing the digits 0-9, as well as a star and a number key. The talk key 152 and the mode key 153 are designed to change the modes of the hand unit 1. The talk key 152 is a non-latching pressure switch and the mode key 153 is a latching slide switch.

Each time the PTT button 152 is pressed, the operation mode of the manual unit 1 is alternately between a talk mode "which establishes a channel to the base unit 2 and enables a telephone call and a standby mode which terminates the channel and switches the handset to standby. In standby mode, when the mode button 153 is in the position shown in FIG. 2 shown basic position, the base unit 2 waits for an outgoing from the handset 1 out call and the receipt of a call from the telephone line. 3 When the mode switch 153 is in a retracted position (opposite to that shown in FIG. 2 shown), the basic unit waits only for an outgoing call from the hand unit 1 and ignores any incoming call from the telephony line 3. The mode key 153 thus activates the handling of outgoing and incoming calls in the same way as in ordinary cordless telephones and standard telephones, but only the handling of outgoing calls is possible in the "withdrawn" position. Pressing the PTT button 152 in the standby mode of the handset 1 places the handset 1 in call mode, allowing the handling of incoming and outgoing calls regardless of the position of the mode button 153. Upon depression of the talk key again, the hand unit 1 returns to the normal or retired standby mode given before the telephone call, as determined by the position of the mode switch.

A random access memory (RAM) stores an identification code ID, which will be referred to later.

In the hand unit 1, an encoder 161 (Fig. 2), under the control of the microcomputer 140, generates a command signal CMND. Similarly, an encoder 251 (FIG. 3) in the basic unit 2 under

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Control by the microcomputer 240, a command signal CMND.

Fig. 4 shows an example of a signal format from which the command signal CMND is formed. The head of the command signal CMND is a bit synchronizing signal BSYN of more than 12 bits (16 bits in this embodiment), followed by a frame synchronizing signal FSYN of 16 bits. These signals BSYN and FSYN have a special bit pattern, such as:

BSYN = 0101010101010101 for all channels;

FSYN = 1100010011010110 for the upper channels; and

FSYN = 1001001100110110 for the lower channels.

After the signal FSYN, the command signal CMND further has a 25-bit identification code ID for identifying the hand unit 1 and the base unit 2 constituting a pair, a 12-bit error correction code ECC for the identification code ID, and an 88-bit control code CTRL, arranged in this order. The control code CTRL includes a code for controlling the opening and closing of the transmission channel between the hand unit 1 and the base unit 2, a code indicating the transmission of the telephone number of the other apparatus (ie, the other party's apparatus), a code which is the same transmitted telephone number indicates, etc. The control code CTRL contains data indicating the type of control (operation code) and data (operand) required for control. For example, when a channel is to be opened, the control code CTRL contains data consisting of a first bit pattern and dummy data, and when a telephone number of the remote station is transmitted, the control code CTRL contains data consisting of a second bit pattern and data related to the telephone number consist.

In the command signal CMND, the synchronizing signals BSYN and FSYN contain non-return-to-zero (NRZ) signals, whereas the identification code ID, the error correction code ECC, and the control code CTRL contain split phase signals (Manchester code) consisting of the NRZ signals are converted. The transmission speed of the signal CMND is set at 1200 bps, for example.

The command signal CMND is applied to the PLL circuit 115 at its creation via the adder circuit 114 (Fig. 2), so that the signal Su is frequency-modulated by frequency-shift keying (FSK) by the command signal CMND.

A squelch detection circuit 162 is connected to the intermediate frequency amplifier 125 and detects the presence or absence of the FM signal Sd in the level of the IF signal. The squelch signal generated thereby SQLC is supplied to the microcomputer 140.

Further, a decoder 163 corresponding to the encoder 161 is connected to the demodulator 126 to extract the command signal CMND transmitted from the basic unit 2. The extracted command signal CMND is supplied to the microcomputer 140.

A ringing tone generator 165 controlled by the microcomputer 140 generates a ringing tone signal upon receipt of a call. The ringing signal is supplied to the speaker 166 of a call set.

The microcomputer 140 supplies the PLLs 115 and 124 with a signal CHNL indicating a channel and the PLL 115 with a signal TXEN for controlling the transmission of the FM signal Su. The microcomputer further supplies the amplifiers 112 and 127 with a signal MUTE for automatic squelch.

A light emitting diode (LED) 167 and an LED unit 168 are also controlled by the microcomputer 140. The LED 167 lights up when the handset 1 is put into conversation mode. The LED unit 168 forms a display which is mounted on the front panel of the hand unit 1 and contains, for example, ten light-emitting diodes, which are arranged in a line and correspond to the number of channels. These LEDs are lit in response to the channel selection data supplied as input from the keyboard 151, etc.

FIG. 3 shows a Steuerschaitung, which is constructed in substantially the same manner as the control circuit 140 of the hand unit 1 and has substantially the same functions. The components 241245 of the control circuit 240, which correspond to the components 141-145 of the control circuit 140, have the same final digits in the reference numeral, whereas the first digit is replaced by 2. For this reason, an explanation of the components 241-245 is omitted. An exception is that the ROM 242, for example, a program 400 as shown in FIG. 5 displayed stores.

Further, a RAM 254 and circuits 261-263 similar to the RAM 154 and the circuits 161163 of the hand unit 1 are provided, and the signals processed by these components of the basic unit 2 are similar to the signals processed by the corresponding components of the hand unit 1, so that their explanation is also omitted ,

A telephone number signal generating circuit 265 controlled by the microcomputer 140 generates a sound coding signal TENC corresponding to the telephone number which the subscriber calls. The signal TENC is supplied to the amplifier 227.

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A relay 266 controlled by the microcomputer 240 via an amplifier 267 controls a relay contact 232.

A ringing detection circuit 268 is connected to the telephone line 3 to detect a ringing tone signal representing an incoming call and to generate a detection signal RGTN which is supplied to the microcomputer 240.

The operation of the hand unit 1 and the basic unit 2 are respectively controlled by the CPUs 141 and 241 in accordance with the programs 300 and 400 of Fig. 5 in the following manner:

When the hand unit 1 is in standby, step 301 is first executed to check the positions of the talk key 152 and the mode key 153. At this time, if the mode key 153 is in normal operation, step 302 is also executed, with the PLLs 115 and 124 being controlled by the CHNL signal to set the upper and lower channels corresponding to the CHNL signal and the detector 162 conducting checking if the FM signal Sd has been received on a first selected lower channel and providing the appropriate signal SQLC depending on the determination. If the signal Sd has not been received on the selected channel, the same operations are performed for the next lower channel. In this way, it is determined by sequentially and repeatedly changing the lower channels whether the FM signal Sd has been received on one of the ten lower channels or not. In step 302, the lower channels are thus repeatedly scanned.

On the other hand, when the basic unit 2 is in standby, the presence or absence of a call arriving from the telephone line 3 is checked by the signal RGTN in step 401. Thereafter, in step 402, the upper channels are sampled as well as the lower channels in step 302.

When the talk key 152 of the hand-held unit 1 is depressed at any time, the hand-held unit's program 300 proceeds to the step 303 where a clear channel is searched by the signals CHNL and SQLC in the same way as in the step 301.

After finding a clear channel, the transmission of the FM signal Su is enabled by the TXEN signal in step 304. Thereafter, in step 305, an identification code ID is read from the RAM 154 and supplied to the encoder 161. The encoder 161 further receives the outgoing call indicating control code CTRL from the microcomputer 140. The command signal CMND including the control code corresponding to the outgoing call is extracted by the encoder 161 and supplied to the adding circuit 114. Thus, in step 306, the command signal CMND is transmitted to the basic unit 2 by the FM signal Su.

The transmission of the command signal CMND in step 306 is repeated for a period of time in which all the channels in the basic unit 2 are scanned at least once assuming that no response has been sent back from the basic unit 2.

As stated above, the basic unit 2 in the standby mode sequentially scans all upper channels in step 402. In the sampling mode, when an upper channel over which the hand-held unit 1 transmits the command signal CMND is found, the signal Su is received by the base unit 2 and sampled by the signal SQLC, and the program proceeds to step 405 to terminate the scan Identification code ID in the signal CMND to specify.

If the identification code ID does not match that in the RAM 254, the program 400 proceeds to step 402. If a match is found, the program proceeds to step 406 where the transmission of the FM signal Sd is allowed by the TXEN signal. In step 407, the command signal CMND is generated in the same manner as in step 305. In step 408, the command signal CMND is then sent back to the hand unit 1 by the FM signal Sd in the lower channel forming a pair with the upper channel used. The control code CTRL in the returned command signal CMND corresponds to that of the command signal CMND generated in step 305. This means that the control code generated in step 305 is reflected by the command signal CMND.

Meanwhile, in step 307, after the generation and transmission of the command signal CMND at step 306, the hand-held unit 1 checks whether or not the proper identification code ID has been returned to it by the output of the decoder 163. In practice, steps 305, 306 and 307 are executed alternately and repeatedly by the program 300 in time-division multiplexing until all channels in the base unit 2 have been sampled or until the return of the correct identification code ID is confirmed.

If it is determined in step 307 that no correct identification code ID has been returned from the base unit 2, the program 300 returns to step 302. Upon confirmation of the return of a correct identification code ID from the basic unit 2 in step 307, the program 300 proceeds to step 308 in which the amplifiers 112 and 127 are decoupled from the squelch condition caused by the signal MUTE and a confirmation code for confirming the return of the control code CTRL generated in step 407 and incorporated into the command signal CMND. The latter

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Signal is sent back to the basic unit in step 309.

In the basic unit 2, the presence of the confirmation code is confirmed in step 409, wherein the relay 266 is driven to connect the conversion circuit 231 via the contact 232 to the telephone line 3, and the amplifiers 212 and 227 are caused by the signal MUTE Noise lockout decoupled.

The hand unit 1 is thus connected via the base unit 2 to the telephone line 3.

When the subscriber inputs the first digit of a desired telephone number via the keyboard 151 of the hand unit 1, the control signal portion CTRL of the command signal CMND contains a code indicating the existence of a telephone number and data relating to the first digit of the telephone number. A control signal CMND containing this information is extracted by the encoder 161 in step 311 and sent to the basic unit 2 in step 312.

In step 411, it is determined in the basic unit 2 whether the identification code ID generated in step 311 in the control signal CMND is correct. If the identification code ID is not correct, the program goes

400 Returning to step 402. If the identification code ID is correct, the program proceeds to steps 412 and 413 in which the command signal CMND generated in step 311 is sent back to the hand unit 1.

Thereafter, in the hand unit 1 at step 313, it is determined whether the identification code ID and the control code CTRL (the code indicating the existence of a telephone number and the digits of the number) in the command signal CMND returned by the basic unit 2 are those generated in step 311 Codes are identical. If the codes are different, the program 300 returns to step 311. If the codes are identical, the command signal CMND is generated with the equality control code CTRL in step 314 and sent to the basic unit in step 315.

The basic unit 2 then generates in step 414 a sound coding signal TENC corresponding to the first digit of the input telephone number from the generator circuit 265 under the control of the microcomputer 240 on the basis of the telephone number-related data included in the handset 1 in step 312, or in this particular case based on the first digit of the telephone number. The signal TENC is output to the telephone line 3 through the amplifier 227, the conversion circuit 231 and the relay contact 232.

Steps 311-315 and 411-414 are repeated each time the subscriber inputs another digit of the phone number of an opponent using the keyboard 151.

By transmitting the TENC signal, the opposite party is called. When he accepts the call, the connection is enabled as described above. This is indicated by the text Phone Conversation State in Fig. 5B.

On the other hand, when a telephone startup from the line 3 arrives, the incoming call is detected at step 401, and subsequently 2 steps are performed in the basic unit according to steps 304 to 309, whereas in the hand unit 1 steps corresponding to steps 405 to 409 are performed , which causes the connection.

During the call connection, the hand-held unit 1 repeatedly checks the operation mode of the talk key 152 in step 321, whereas the basic unit 2 repeatedly checks in step 421 whether or not the identification code ID is present and correct.

When the talk button on the handset 1 is depressed at the termination of the call, the program 300 proceeds to step 322, in which the amplifiers 112 and 127 are switched to squelch by the MUTE signal and the command signal CMND which terminates the control code CTRL has an end code indicating a call connection is extracted by the coder 161 in step 323 and sent to the basic unit 2. Upon receiving this command signal CMND in the basic unit 2, it is determined in step 421 whether the identification code ID in the command signal CMND is correct.

If the identification code ID is correct, the command signal used in step 322 is returned to hand unit 1 in steps 422 and 423.

In hand unit 1, it is then determined in step 324 whether the identification code ID in the returned command signal CMND is correct. If the identification code ID is correct, the command signal CMND, which indicates the confirmation of the returned command signal CMND, is generated in step 325 and sent to the basic unit 2 in step 326.

Upon confirmation of the command signal CMND in step 424, the program 400 in the basic unit 2 proceeds to step 425 where the transmission of the FM signal Sd is interrupted by the signal TXEN and the amplifiers 212 and 227 are put into the squelch mode by the signal MUTE be set. In the subsequent step 426, the relay contact 232 is disconnected or opened and the base unit 2 is set in an on-hook state. The program 400 then returns to the step

401 back.

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In the hand-held unit 1, in step 327, after the command signal CMND is sent to the basic unit 2 in step 326, the transmission of the FM signal Su is interrupted by the signal TXEN and the amplifiers 112 and 127 are set in the squelch operation by the signal MUTE. The program 300 then returns to step 301.

By the method described above, the hand unit I and the basic unit 2 are reset to the standby mode.

The above explanations are an explanation of the basic structure and operation of a conventional cordless telephone using an identification code ID.

In such a cordless telephone, when the identification code ID of the hand unit 1 corresponds to that of the basic unit 2, a conversation channel is formed and the subscriber can make a call, whereas if the identification codes are unequal, no conversation channel is established and problems such as wiretapping or tapping the conversation unauthorized third parties are avoided.

However, in a cordless telephone operating with an identification code ID, problems may occur in the circuit for generating the identification code ID.

In particular, the hand unit 1 is cordless and therefore equipped with a built-in dry battery, which serves as a power supply. Even if the hand-held unit 1 is not used for a telephone call, part of its circuit becomes like the control circuit 140, etc. energized and operated. For this reason, when using a usual dry battery as the power source for the hand unit 1, the cost of the power supply would be extremely high. As a voltage source, therefore, a rechargeable battery such as a nickel-cadmium battery is used, so that when the battery is exhausted, the hand unit 1 as shown in FIG. 6 shown in a predetermined position on the base unit 2 to charge the built-in hand unit 1 battery.

If the identification code ID is stored in the RAM 154 in the hand unit 1, the ID code is lost when the battery is exhausted because the memory 154 is volatile.

Therefore, when the battery in the hand-held unit 1 is exhausted or a subscriber buys a cordless telephone, it is necessary to send the identification code ID from the base unit 2 to the hand-held unit 1 to re-store it in the RAM 154 or to update it bring to.

Japanese Laid-Open Patent Publication No. 62-26937 (corresponding to Japanese Patent Application No. 60-166107) proposes a solution to this problem by placing the hand-held unit 1 of FIG. 6 on the base unit 2. This cordless phone is characterized by the following features:

(i) A charging current flows through charging contacts (terminals) from the base unit 2 to the hand unit 1;

(ii) The identification code ID shall be issued by a terminal specially designed for this purpose by the

Basic unit 2 transferred to the hand unit 1;

(iii) The hand-held unit 1 stores the identification code ID in its reception in the memory and returns the received identification code ID to the basic unit 2 via a transmission channel;

(iv) The basic unit 2 checks the returned identification code ID to see if it corresponds to the identification code ID sent to the hand unit 1.

It is thus necessary that the base unit 2 and the hand unit 1 of this cordless telephone are respectively provided with two charging terminals and one ID code terminal.

This is also the case with a cordless telephone according to EP 176 855 A3.

However, as the number of terminals increases, reducing the size of the basic unit 2 and the manual unit 1 becomes much more difficult. Moreover, it is not expected that all terminal pairs are kept in contact with their counterpart with the same contact pressure at several pairs of terminals. It is even possible that due to normal manufacturing tolerances some of the terminal pairs are exposed to contact pressure which is insufficient for proper contact. It is thus likely that, as the number of terminal pairs is increased, it goes without saying that the number of out of tolerance bad contacts is also increased.

The object of the invention is to provide a cordless telephone, which has no separate connection for transmitting the identification code to the phone and thus has a smaller number of terminals.

It is a further object of the invention to provide a cordless telephone, which can be reduced in size due to the smaller number of terminals.

Moreover, it is an object of the invention to provide a cordless telephone which is less prone to errors than conventional cordless telephones when the identification code is transmitted from the base unit to the handset to be stored there in a memory.

According to the invention this is achieved in a cordless phone of the type mentioned by the characterizing features of claim 1.

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The proposed measures ensures that the transmission of the identification codes also takes place via the contacts serving to charge the rechargeable device, such as a battery. As a result, can be dispensed with additional contacts for the transmission of the identification codes, whereby a considerably higher contact reliability is achieved and a reduction in the volume of the cordless telephone is made possible.

Due to the features of claim 2, there is the advantage of a very extensive maintenance freedom of the chargeable device.

In a cordless telephone according to the invention, in which the base unit carries the hand unit during charging of the rechargeable device, it is advantageous if the first and the second charging contact are in communication with each other, wherein the hand unit is separated from the base unit in the construction of the transmission channel and the first charging contact is disconnected from the second charging contact. This ensures that the rechargeable unit can always be recharged when the base unit carries the hand unit.

Due to the features of claims 4 and 5 results in a very simple construction of the charging detection circuit.

In order to allow easy access to the identification code, it is advantageous to design the first memory as a random access memory.

Due to the features of claim 7 results in a very simple construction of the charging circuit.

Further features and advantages of the invention will now be described with reference to the following detailed description of a circuit of an exemplary embodiment of a cordless telephone according to the invention with reference to the accompanying drawings.

In the drawings show:

FIG. 1 is a perspective view showing the operation of a hand unit and a base unit; FIG.

FIG. 2 is a block diagram of the overall circuit of a hand unit of a conventional cordless telephone; FIG.

FIG. 3 is a block diagram of the overall circuit of a basic unit of a conventional cordless telephone; FIG.

FIG. 4 is a diagram showing a signal format usable for transmission; FIG.

FIGS. 5A and 5B are a flow chart showing the sequence of operations performed by a conventional hand-held unit and basic unit;

Fig. 6 is a perspective view of an apparatus showing a state where the hand unit is set on the base unit to charge the battery;

FIG. 7 is a schematic circuit diagram of the overall circuit of an embodiment of the invention; and FIG

FIG. 8 is a flow chart showing a sequence of actions performed by the embodiment of the invention shown in FIG.

In the basic unit 2 of FIG. 7, a power supply 272 is supplied with a mains transformer, a rectifier, etc. via the connector 271 with a local AC voltage and this is converted to a predetermined DC voltage. The DC voltage thus obtained is supplied to each part of the basic unit as an operating voltage and to the charging voltage output contact 278 via a charging circuit 273.

The charging circuit 273 is composed of, for example, the transistors Q1 and Q2. In particular, between the output terminal of the power supply 272 and the contact 278, a resistor R1 and the collector and the emitter of the transistor Q2 are connected in series, whereas the diodes D1 and D2, a resistor R2 and the collector and the emitter of the transistor Q2 in series between the output terminal of the power supply 272 and ground are connected. The base of the transistor Q1 is at the connection point between the diode D2 and the resistor R2, and the base of the transistor Q2 receives a control signal (terminal output) TXID from a control circuit 240 via a resistor R6. The signal TXID is normally high (H ") and is set to a value corresponding to a command signal having a specific control code CTRL when the identification code ID stored in a memory of the hand-held unit 1 is updated or confirmed.

A charging voltage detection circuit 274 is connected between the output of the power supply 272 and ground, with a resistor R4, the emitter and the collector of a transistor Q3, and a voltage regulation diode D3 connected in series. The base of the transistor Q3 is connected through a resistor R3 to the collector of the transistor Q1. The collector output signal CHRG of the transistor Q3 is supplied to an interruption input INT of the control circuit 240 (which has a microcomputer such as a U.PD75104 manufactured by NEC Corporation). A common contact 279 is connected to ground.

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In the hand-held unit 1, a low-impedance rechargeable battery 171, for example, a nickel-cadmium battery, supplies its output voltage as the operating voltage to each part of the hand-held unit t. A charging voltage input contact 178 is connected to the battery 171 via a light-emitting diode (LED) D5 of an opto-coupler PC.

The optocoupler PC is included in a detection circuit 175. Between the positive terminal of the battery 171 and ground, a resistor R5 and the collector and the emitter of a phototransistor Q5 of the optocoupler PC are connected in series. The collector output of the transistor Q5 is inverted by the inverter 176, and the inverted output RXID is supplied to an interrupt input INT of a control circuit 140 (which uses a microcomputer such as a U.PD75108 of NEC) and a terminal Ql as a terminal input.

The contact 178 and the ground terminal 179 in the hand unit 1 are arranged so as to cooperate with the contacts 278 and 279 in the basic unit 2, respectively, when the battery 171 is charged.

The ROM memory 142 (FIG. 2) of the control circuit 140 in the hand unit 1 stores an interrupt subroutine 10 of FIG. 8, whereas the ROM 242 (FIG. 3) of the control circuit 240 in the basic unit 2 stores an interrupt subroutine 20, FIG. which is also shown in Fig. 8 stores.

In the construction described above, the contact 278 is open when the hand unit 1 is not set on the basic unit 2, so that the collector current of the transistor Q1 can never flow regardless of the signal TXID. The transistor Q3 is therefore off and the collector output CHRG is low (L). When the collector output signal CHRG is at low level L, it does not interrupt the control circuit 240 even when it is supplied to the interruption terminal INT.

In addition, since the contact 178 is also open when the manual unit 1 is not set to the basic unit 2, the diode D5 does not light up, the transistor Q5 is accordingly turned off and the inverted signal RXID is at the level L. The control circuit 140 becomes therefore not interrupted in this case.

The hand unit 1 and the base unit 2 is in this case ready for the subscriber to make an outgoing call and receive an incoming call, ie, to be able to communicate via the cordless telephone.

However, when the hand unit 1 is set in the predetermined position on the base unit 2 (FIG. 6), the contacts 178 and 179 contact the contacts 278 and 279, respectively, as shown in FIG.

Since the control signal TXID is at a high level, the transistor Q2 and thereby the transistor Q1 are turned on. The collector current of transistor Q1 therefore flows through contact 278, contact 178 and LED D5 to battery 171 which in this manner is charged by the regulated, constant collector current from transistor Q1.

Accordingly, when the collector current flows in the transistor Q1, the transistor Q3 is turned on, so that the signal CHRG becomes high and the control circuit 240 interrupts.

When the control circuit 240 is interrupted, the CPU 241 (Fig. 3) of the control circuit 240 monitors the execution of the subroutine 20 (FIG. 8) with step 21 to prevent subsequent interruptions. In step 22 (FIG. 8), the operation of the basic unit 2 is then delayed by a predetermined duration. The delay provided in step 22 is chosen so that the operation of the basic unit 2 is delayed until the charging of the battery 171 is completed and each part of the manual unit 1 can be normally operated due to a flowing charge. At the time of completion of step 22 so already every part of the manual unit 1 operates in normal operation.

Thereafter, the subroutine 20 executed by the CPU 241 proceeds to step 23, in which a new identification code ID based on, for example arbitrary numbers and stored in RAM 254. In step 24, a free channel is searched as in step 303. After finding a free channel, the command signal CMND is generated in step 25. In this case, the control code CTRL in the command signal CMND contains data indicating a transmission on the free channel and data related to the number of the free channel found in step 24. The identification code ID in the command signal CMND is the newly generated in step 23 identification code.

In step 26, the command signal CMND generated in step 25 is then supplied to transistor Q2 as signal TXID. The transistor Q2 is ON / OFF controlled in its conducting state by the command signal CMND generated and supplied thereto in step 25, so that the charging current for the battery 171 is also ON / OFF controlled by the command signal CMND via the contacts 278 and 178.

Meanwhile, starting from the time of putting the hand unit 1 on the base unit 2, the charging of the battery 171 starts, so that the LED D5 lights up substantially instantaneously by the charging current.

AT 403 104 Β

When the charging has progressed so far that each part of the hand unit 1 is normally operable, the lighting of the LED D5 is detected by the transistor Q5, so that the signal RXID becomes high level and is supplied to the interruption terminal of the control circuit 140 to interrupt it.

After interrupting the control circuit 140 by the signal RXID having the level H, the CPU 141 starts the running of a subroutine 10 (Fig. 8) with the step 11, in which subsequent interruptions are prevented. In step 12, the signal RXID supplied as a terminal input is then received by the control circuit 140. At this time, the light emitting diode D5 receives the charge current for the battery 171 and is turned on and off by the command signal CMND transmitted in the step 26, so that the signal RXID corresponds to the command signal CMND. That is, the command signal CMND is sent from the base unit 2 via the contacts 278 and 178 to the hand unit 1 and supplied to the control circuit 140 as the signal RXID.

If it is determined in step 12 that the signal RXID corresponds to the command signal CMND, the transmission of the FM signal Su is enabled in step 13, and in step 14 the identification code ID and the control code CTRL are extracted from the command signal CMND transmitted in step 26. In step 15, this command signal is then reflected back to the basic unit 2 by the FM signal Su via radio waves. The channel for transmitting the FM signal Su is selected from idle channels on the basis of the idle channel data transmitted in step 26 as part of the control code CTRL included in the command signal CMND.

After the return of the command signal CMND, the transmission of the FM signal Sd is blocked in step 16.

The FM signal Su is received by the basic unit 2, and in step 27, it is determined whether the identification code ID included in the command signal CMND returned from the FM signal Su in step 15 is the identification code ID sent to the hand unit 1 in step corresponds; That is, it is determined whether the identification code ID has been correctly returned to the basic unit 2. If this has been sent back correctly, the generation of the command signal CMND, which indicates the confirmation of the ID code and is sent to the hand unit 1 in step 29, takes place in step 28. The command signal generated in step 28 is transmitted via the signal TXID as well as in step 26 via the contacts 278 and 178.

Upon receipt of this command signal CMND by the hand unit 1, the identification code ID received in step 26 is stored in the RAM 154 in step 17. Thereafter, in step 18, the interruption caused in step 11 is released and the subroutine 10 is terminated.

The subroutine 20 is also terminated after the disablement of the interrupts inhibited in step 21 has been completed in step 31.

If it is determined in step 27 that the identification code ID contains errors, the program jumps to step 31.

The battery 171 is charged by the regulated constant current, and after lapse of a predetermined charging period, the signal TXID goes to a low level and the transistor Q1 turns off, thereby stopping the supply of the charging current to the battery 171.

In the embodiment of the invention described above, when the hand unit 1 is seated on the base unit 2 for charging its battery 171, the identification code ID is updated or confirmed. In this case, a new identification code ID sent from the base unit 2 to the hand unit 1 is sent back from the hand unit 1 to the base unit 2, so that it can be determined whether the new identification code ID sent to the hand unit 1 is correct. In this way, in a device constructed according to the invention, the storage of a false identification code ID in the memory of the hand unit 1 is avoided.

It is to be noted that the identification code ID is transmitted through the charging terminals 278 and 178 from the basic unit 2 to the hand unit 1, so that no own terminals are necessary for transmitting the identification code ID and, accordingly, the number of terminals can be reduced. The transmission of the identification code ID via the charging ports also provides easy and accurate access to the identification code ID.

To further reduce the number of ports, the identification code could also be sent over a transmission channel. In this case, however, there is no saving, since two pairs of contacts are required in any case for charging the hand unit 1 via the basic unit 2. Further, if another cordless telephone nearby uses the same channel, this phone could respond to transmitted identification code, whereby the identification code ID could not be recorded in the correct hand unit 1 and the identification code ID in the hand unit 1 of the other cordless telephone is wrong could be adjusted.

AT 403 104 B

In contrast, according to the invention, the identification code ID is sent from the base unit 2 via the terminals 278 and 178 to the hand unit 1 and sent back to the base unit 2 via a transmission channel from the hand unit 1. Furthermore, the terminals for transmitting the identification code ID are also used as charging terminals 178 and 278, so that only two pairs of contacts are needed: the contacts 278, 178 and 279, 179, which are the same two pairs of contacts as are needed in each case for charging the battery 171. The transmission of the identification code ID is carried out safely and reliably in this way. Further, the transmission channel is used only to transmit the identification code ID from the hand unit 1 to the base unit 2, so that the transmission of the identification code ID is not affected by other cordless telephones used nearby. The identification code ID is reliably transmitted from the hand unit 1 to the base unit 2 in this way.

The basic unit 2 searches for a free channel and supplies the hand unit 1 with data indicating this free channel and the identification code ID. The identification code ID can be sent back in a relatively short time as compared to the case where both the hand unit 1 and the base unit 2 search a clear channel to form a transmission channel to make an outgoing call or to receive an incoming call.

Since the hand-held unit 1 returns the identification code ID error-free via a free channel, the transmission is not disturbed by other radio waves. Further, the hand-held unit 1 does not need to broadcast the FM signal Su more than necessary to return the identification code ID.

In a variant of the preferred embodiment of the invention described above, the identification code ID stored in the hand-held unit 1 is compared with the original identification code ID in the basic unit 2 while the hand-held unit is mounted on the base unit 2 in substantially the same manner as FIG described above in connection with subroutines 10 and 20. However, the original identification code ID in the basic unit 2 is returned to the hand-held unit 1, and the hand-held unit 1 and the base unit 2 communicate with each other only in the manner described above, when a discrepancy between the identification code ID stored in the hand-held unit 1 and the original one Identification code ID in the basic unit 2 consists.

For example, the LED D5 (FIG. 7) may also be connected between the collector of the transistor Q1 and the contact 278, whereby the contact 178 may be connected directly to the battery 171 and the light emitting diode D5 and the transistor Q5 may be arranged so that they are optically interconnected when the hand unit 1 is placed on the base unit 2.