Telephone line interface circuitry for telecommunications equipment.

[Brief Description of the Drawings]

In a drawing, Drawing 1 is a circuit diagram of the outline of the 1st embodiment of the present invention, and Drawing 2 is a circuit diagram of the optional alternative feature of the present invention. Detailed explanation of an exemplary embodiment The exemplary circuit of the present invention is shown in Drawing 1. As shown in a figure, terminals 1 and 2 of interface circuit 10 connect although telephone wire illustration of usual modem (modem) circuit 12 and the telephone subscriber is carried out, while the number is not attached. The A tip conductor (T) and ring conductor (R) of the telephone wire are connected to input nodes 14 and 16 of all the wave diode bridges 18 which consist of diode 18A-18D via terminals 1 and 2 at each. The negative pole with diodes 18A and 18D is connected together, and forms the positive output node of the bridge, and the node with diodes 18B and 18C is connected together, and forms the negative output node of the bridge. Although a right course is left for a time, when the relay station is seen from a subscriber line, in each of a A tip conductor and a ring conductor, Connected is visible [ a public telephone circuit network ] to about 200-ohm impedance and series as direct-current potential which is intermediary To have about 48~50V. a member's telephone or other devices connect with a telephone wire -- having (that is, electrically connected by carrying out "off-Hook") -- you complete the circuit over a A tip conductor and a ring conductor, and about 20~100-mA current makes it make it flow via the telephone wire and the member's device A member's device (namely, CPE) detects this current as a proof which is off-Hook, and the device of a relay station begins the suitable operation depending on whether the member's having started A call or a telephone call is answered. When the customer has started A call, after the customer or its device for a dial carries out off-Hook and catches a telephone wire, it dials the telephone number of an address. Two models which dial are used. It is with a tone dial and a dial pulse. When a dial pulse is used, line current is intermittent at about 10 times (namely, pulse) of a rate in 1 second. Discontinuation of the line current of most continuation time is treated as directions of on-Hook which asks for Disconnection from the telephone wire. By use of bridge 18, electric power comes to be supplied to an interface circuit from a telephone wire, and it enables use of a bipolar or MOS art if needed. Since it leaves sufficient voltage to supply electric power in an interface circuit, about 1.2-v voltage drop between the diodes of bridge 18 is permissible. And the sum of the voltage drop and the voltage drop between the both ends of an interface circuit does not need to exceed simultaneously the voltage drop between the A tip conductor in an OFF hooking state, and a ring conductor which can be permitted. Transistor 20 corresponds to the off-Hook relay used by conventional technology, and it acts as fixed load with the related current setting circuit, and gives an equivalent thing electronically [ an ordinary line locking coil ]. The circuit (namely, capacitor 34) which will control transistor 20 if transistor 20 is made to turn ON by the method described below, The exchange signal ingredient between the bridge nodes 24 and 26 is disregarded so that the high impedance of exchange may be given between bridge connection points, i.e., bridge node 24 and 26. However, it is only that related emitter load resistance 22 and in-series low collector emitter resistance exist to a direct current. Therefore, a ring conductor serves as a passage of impedance low only for a direct current from a A tip conductor through bridge 18, transistor 20, and resistance 22. This passage is suitable to make a A tip conductor and a ring conductor produce the 20-mA minimum direct-current mesh currents needed. Exchange impedance (they are 600ohms of nominal value by agreement) is attained by the in-series passage with capacitors 32 and 34 containing the winding of related transformer 36. By the high impedance of this exchange, and the low impedance of a direct current, a load circuit is similar to an inductor which is usually used to a telephone wire maintenance function. Since it will give the high impedance of a direct current again and the remaining circuits will send only very slight current if transistor 20 is intercepted, mesh currents fall in 0 mA or less, and, as for the device of a relay station, CPE interprets the state as it being "on-Hook." In this way, the object that transistor 2 and its control circuit are double is served. That is, it adds to a line maintenance function and they are To works as on-Hook / off-Hook relay, or a switch, i.e., a hook switch. The rebound to a Mechanical contact and the problem of switching of a relay like the early makeup break demand of a dial pulse are avoided by arrangement of this switching. if transistor 20 is turned ON -- a certain predetermined time -- the diode of bridge 18 -- exactly, bias of either of two pieces, i.e., diodes 18A and 18C, or diodes 18B and 18D is carried out to a forward direction, and it flows through it. On the other hand, bias of other two diodes is carried out to an opposite direction. The pair of the diode by which bias is carried out to a forward direction is dependent on the polarity of the A tip conductor and ring conductor in relation to nodes 24 and 26. However, telephone and data-communications apparatus are dependent on the voice frequency signal of exchange of both for information transmission. These exchange signals are small amplitude as compared with the line current of a direct current, and are superimposed by the line current of the direct current. And since bias of the diode is already carried out to the forward direction, it passes along an exchange signal, without being interfered with a bridge. in this way, an exchange signal should pass bridge 18 and direct-current prevention capacitors 32 and 34 (the low impedance of exchange is given with voice frequency) in between one winding of joint transformer 36 of one A tip conductor and a ring conductor, and another side -- it passes freely. Operation of transistor 20 is controlled by on-Hook / off-Hook signal given to line 38 by the circuit (not shown from the portion of the present invention not being constituted but it being in the CPE) from the line capture switch in CPE to Opt isolator 40. Opt isolator 40 contains light emitting diode (LED) 44 relevant to photo-transistor 42. if the signal on line 38 is given in the 1st (for example, -- low) state. LED44 is turned on, carries out the electrical connection of the photo-transistor 42, and, thereby, connects the base of transistor 48 to the spot weld of resistance 56 and capacitor 34 effectively. Thereby, transistors 48 and 20 are set to ON. The transistors 48 and 20 are arranged by the Darlington connection of high gain. Although resistance 46 is the bias resistance to grounding from the base of transistor 48, the value must be so low [ resistance ] enough that the voltage which arises as the result does not turn on the transistor concerned, when the current which passes along the resistance is dark current of a photo-transistor. The voltage between the both ends of resistance 46 reduces the base emitter junction voltage drop of transistors 48, 42, and 20, appears among the both ends of resistance 22, and sets up the emitter current of transistor 20. Next (the collector emitter voltage of Opt transistor 42 was reduced), the voltage between the both ends of capacitor 34 gives voltage to resistance 46. While giving high gain and having given the load which can be disregarded among the both ends of capacitor 34, transistor 20 turns on and turns off work of a darling transistor quickly. Luminescence of LED44 will connect zener diode 58 and capacitor 34 to the base of transistor 48 via transistor 42. Resistance 56 gives charging current to capacitor 34. In this way, after charge of capacitor 34, capacitor 34 operates so that fixed voltage may be kept essential to the base of transistor 48, and it gives fixed line current via transistor 20 and resistance 22. When the call signal of a telephone is received by a A tip conductor and the ring conductor, the voltage between bridge nodes 24 and 26 increases notably, and then zener diode 58 is switched and turned on. This connects bridge node 26 to one terminal of transformer 36 directly, and it makes it vibration of voltage appear among the both ends of a transformer. Vibration of this voltage is detectable as a proof of the call signal of a telephone by a side other than a transformer. In addition to being a line capture (namely, on-Hook / off-Hook) signal, in the case of a dial pulse, the work as a dial signal performs similarly the signal given to line 38. Capacitors 36A and 36B are free choice-like, and it may be used in order to compensate the amount of reflective attenuation in transformer 36. In this way, line current itself gives the electric power which drives an interface circuit irrespective of whether CPE is turned on or not. It is only that CPE controls on-Hook / off-Hook signal given to line 38. On-Hook / off-Hook signal is given by the relay or switch which has one point of contact connected to line 38, and another point of contact connected on the way to for giving 5V to LED44. CPE is turned off, namely, the point of contact of the relay or a switch becomes being on-Hook with Open, and, so, LED44 can stop luminescence. If CPE becomes off-Hook, the point of contact will close, and will turn ON LED, and then will turn ON photo-transistor 42. The additional feature is shown in Drawing 2. In Drawing 2, voice switch 70 is added to the circuit of Drawing 1. This is for connecting a telephone wire to telephone (for voice communications). The circuit of Drawing 1 is not repeated for the lucidity of a display. The prior art of the switch is objectively electronic. Generally the prior art has adopted a mechanical switch like a relay. This switch like the switch of transistor 20 is controlled via Opt isolator 72. The switch generally shown by 70 is placed in series between telephone (although not illustrated, shown as a thing connectable with lines 68 and 69), and ring conductor R (namely, terminal 2). Line 68 is connected to the 1st node of diode bridge 74, and a ring conductor is connected to the node of the side opposite to the bridge. Tentatively connection of Dorain of FET switching transistor 64 and sauce which are field effect transistors (FET) is made in two nodes of everything but a bridge again, Tentatively connection also of the circuit and zener diode 67 which control FET64 switching transistor is made in two nodes of everything but a bridge again. The latter, i.e., a zener diode, is completely for the protection to excess voltage. The circuit which controls FET64 switching transistor includes Opt isolator 72 and bias resistance 66. If CPE carries out off-Hook, Opt isolator 72 is turned ON and turns off FET switching transistor 64, and as a result, switch 70 will serve as OFF and, thereby, will separate telephone from a telephone wire. On the contrary, when CPE carries out on-Hook, Opt isolator 72 is turned off and FET64 switching transistor is turned on via bias resistance 66 of high resistance. Of course, telephone is connected to a telephone wire by it via a diode bridge and FET64 switching transistor. CPE takes out the signal on a telephone wire using transformer 36 which separates it from a telephone wire, and gives standard "off-Hook" and "on-Hook" to line 38. thus -- although the exemplary embodiment of the present invention has been described -- various change, modification, and improvement -- a person skilled in the art -- an intermediary -- probably, an easy thing will be clear. Such a clear change, modification, and especially improvement plan to be connoted although not stated above. It is in soul of the present invention, and a range. Therefore, the above-mentioned study does not have intention of the restrictive thing, What is it? et al., only by an exemplary thing. That is, the present invention is restricted by only the thing equivalent to the range of the following claims, and it, and is defined.