JPH03187551A - Telephone terminal equipment - Google Patents

Abstract

PURPOSE:To make a call by a telephone set not to require an juxtaposed commercial power source by holding a telephone line for fixed time even when service interruption is generated during the call. CONSTITUTION:When the service interruption is generated in the state of already terminating the call, a transistor 34 is conducted and the base power supply of a transistor 36 for incoming call passes through this transistor 34 although it flows to a photocoupler 33. Namely, transistor 36 and 39, photocoupler 33 and transistor 34 form a loop and become a self-holding circuit. Therefore, even when the input current of the photocoupler 33 to control the call incoming is extinguished by the service interruption, the circuit continues the call incoming. Thus, since the connected state of the telephone line is held for the fixed time even when the service is interrupted during the call, the call can be continuously made by the telephone set to be operated by power to be supplied from the juxtaposed telephone line.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a telephone terminal device.

(Prior Art) Conventionally, the interface circuit of the IT telephone line of a telephone terminal device that operates on commercial power supply can be roughly divided into the circuits shown in Fig. 4 and 5.
There is a method shown in the figure.

A conventional telephone terminal device will be described below with reference to the drawings.

In FIG. 4, 1 is a telephone jack, 2 is a telephone line closing relay, and 3 is an isolation transformer, which isolates the power supply in the circuit from the telephone line. An alternating current signal from the telephone line is output to the terminal 4, and if a signal is applied here, this alternating current component is sent to the telephone line. 5 is a commercial power supply, 6 is a power switch, and 7 is a conversion circuit that generates DC power from the commercial power supply, which outputs 5V here. The telephone line closing relay 2 operates with 5V power from the DC power supply 7. Reference numeral 8 denotes a control means, which is constituted by a microprocessor, and 9 is a transistor.

In FIG. 5, the same reference numerals as in FIG. 4 indicate the same components, and 10 is a diode bridge, 11 is a telephone line closing transistor, and 12 is a control transistor.

In the configuration shown in Figure 5, the commercial power supply and telephone line are the DC power supply 7.
DC nl source 7 which is isolated by but drives the equipment
and the electric t8vij line have a common ground.

The signal on the telephone line is determined to have a positive or negative direction by the diode bridge IO, and has a positive potential with respect to GND of the 5V power supply. Incoming calls to the telephone line are carried out by the control means 8 causing a positive current to flow through the base of the transistor 12, thereby making the transistor 11 conductive.

In the configuration shown in FIG. 4, the relay 2 operates with 5V DC power output from the commercial power supply 5. The relay 2 is activated by a signal output from the control means 8.

The telephone line is set in a closed state, but if a power outage or instantaneous power outage occurs during communication on the telephone line, the power to drive the relay 2 is no longer supplied, and the relay 2 is disconnected, cutting off the connection with the telephone line.

In the method shown in FIG. 5, during a call, the control means 8 applies a base current to the transistor 12, and when the transistor 12 is turned on, the transistor 11 is turned on and the telephone line is closed, but power outages and instantaneous power outages occur. If so, the control means 8 will no longer be able to apply the base current, and the connection with the telephone line will be lost and the telephone will be disconnected.

As mentioned above, telephone terminal devices that use commercial power supply
Since the telephone cannot be used during a power outage, a telephone set that operates only on the current supplied from the telephone line was used in conjunction with the telephone line, as shown in Figure 2.

(Problem to be Solved by the Invention) However, with the above configuration, even if a telephone that operates only with the current supplied from the telephone line is installed, if a power outage occurs while the telephone terminal is in the middle of a call, the call will be interrupted. This had the problem that it would break.

The present invention has been made in view of the above-mentioned prior art, and by maintaining the telephone line for a certain period of time even if a power outage occurs during one call, it is possible to make a call using a telephone that does not require an attached commercial power source. The present invention provides a telephone terminal device.

(Means for Solving the Problems) To achieve this object, a telephone terminal device of the present invention includes:
a power supply circuit that supplies power from a commercial power source; a power outage detection circuit that detects a power outage of the commercial power source; a closing circuit that connects and disconnects a telephone line; and switching means for controlling the closing means to maintain the closed state of the telephone line when the power failure detection circuit detects a power failure of the commercial power supply.

(Function) According to this function, when the power outage detection circuit detects a power outage in the commercial power supply while the closing means is closing the telephone line, the closing means will switch to 1!
! The switching means controls to maintain the closed state of the speech line.

(Example) An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows an interface section of a telephone terminal device with a telephone line in an embodiment of the present invention. 1st
In the figure, 18 is a telephone transformer, which insulates the telephone line from the power supply of the control system.

19 is a telephone jack, 20 is a diode bridge, and 21 is an AC adapter jack, with the inside being positive and the outside being negative. 22 is a reverse connection prevention protection diode, 23 is a 5V regulator circuit, and 24 is a power failure detection/18 circuit, which also serves as a timer circuit after a power failure. Further, 30 and 33 are photocouplers, 32 is an incoming call circuit, and 37 is an attached telephone incoming call detection circuit.

The operation of the telephone terminal device configured as described above will be explained below.

First, in the power failure detection circuit 24, when the commercial power supply is normally applied and voltage is applied to the terminal 21 from the AC adapter, the capacitor 29 is set to 0.0. It is charged with a voltage minus 5V. Therefore, the emitter and base of the transistor 25 are reverse biased and are off. For this reason, the Darlington type photocoupler 3
No current flows through the input terminal 0, and the photocoupler 30 is off.

However, when the commercial power supply stops, the regulator circuit 23
The 5V output from the terminal 31 also stops, and the voltage at the terminal 31 decreases due to current consumption in another circuit not shown in FIG.
Current flows from the emitter of transistor 5 to the base of resistor 27, and transistor 25 turns on.

The photocoupler 30 detects a power outage and performs a timer operation by conducting the photocoupler 30 for a predetermined period of time due to the electric charge of the capacitor 29.

Next, the operation of the interface circuit will be explained.

The signal on the telephone line from the telephone jack 19 is unified in potential direction by the bridge 20 and sent to one incoming circuit 32.
The transistor 34 of the 0 incoming circuit 32, which is applied to the 0 signal, is normally off, and when a positive voltage is applied to the terminal 35 and the photocoupler 33 is turned on, the transistor 36 becomes conductive and enters the incoming state. When the photocoupler 33 is off, the transistor 36 is also non-conductive and no incoming call is received.

However, if the transistor 34, which is normally off, turns on, a call will be received even if the photocoupler 33 is off.

The next annex telephone incoming call detection circuit 37 is a circuit that detects incoming calls from the annex telephone. In FIG. 2, it is assumed that only this telephone terminal device receives a call on the line. The current from the telephone line is
Emitter of transistor 39, base, diode 4o
, resistors 41 and 42, and transistor 39 is on. As shown in FIG. 3, the potential of the emitter of the transistor 39 is such that the audio signal is superimposed on the DC voltage of the line. The base current of this transistor 39 is influenced by the audio signal by the capacitor 38. The capacitance of the capacitor 43 has a large value, and its voltage is very stable as shown in FIG.

At this time, if the attached telephone is connected to the line, the attached telephone also consumes current, causing the line voltage to drop. Accordingly, the emitter of transistor 39 ffi <-tz
falls immediately as shown in FIG. 3, but since the capacitor 43 has a large capacity and falls slowly, the former potential and the latter potential are temporarily reversed. During this period of reversal,
The base and emitter of the transistor 39 are reverse biased and turned off. Only during this time, no voltage from the line is applied to the photocoupler 30.

In this way, the attached telephone detects that a call has arrived on the line.

Next, the operation of each circuit will be explained based on actual operation.

When the commercial power supply is normal, the transistor 25 is off;
Photocoupler 30 is off. If the terminal 35 is low, there is no incoming call on the line of this interface. When the terminal 35 becomes high by a hook switch or the like, the photocoupler 33 becomes conductive, the transistor 36 becomes conductive, and an incoming call is established. As described above, the transistor 39 also has a base current flowing therethrough and remains on. Since photocoupler 30 is still off, the base of transistor 34 is at the same potential as the emitter and is also off. When terminal 35 is returned to low, one interface is separated from the line.

In other words, when there is no power outage, etc., the circuit operates exactly the same as the conventional circuits shown in FIGS. 4 and 5.

If there is a power outage while this interface is receiving a call, the transistor 25 will turn on and the photocoupler 30 will turn on.
is also conductive. At this time, the transistor 39 is also on, so the current of one line flows through the transistor 39° photocoupler 30.
The current flows through the output side of the transistor 34, the base of the transistor 34, and the emitter.

As described above, if a power outage occurs while a call has already been received, the base current of the transistor 36 for zero reception, which turns on the transistor 34, will now pass through the transistor 34 instead of flowing through the photocoupler 33.

In other words, transistor 36.39, photocoupler 30
, transistor 34 forms a loop and serves as a self-holding circuit.

Therefore, even if the input current of the photocoupler 33 that controls incoming calls disappears due to a power outage, this circuit continues to receive incoming calls. Therefore, even if there is a power outage, your phone will not be disconnected.

Thereafter, as shown in FIG. 2, when the attached telephone 16, which can be used even during a power outage, is picked up, the voltage of the telephone line drops and the transistor 39 is turned off as described above.

Then, the self-holding circuit for receiving calls is cut off, and this interface stops receiving calls. As a result, power outage telephone 1
6, and since this interface has stopped receiving calls, there will be no impedance mismatching with the telephone line.

In the above-described self-holding circuit for incoming calls, even if the power outage or instantaneous power outage is restored, the photocoupler 30 is turned off and no loop is formed. This allows the terminal 35 to control incoming calls.

Furthermore, if the self-holding circuit continues to receive calls due to a power outage, there will be problems such as ttta not being received from outsiders, so when the capacitor 29 is no longer charged, the photocoupler 30 will be turned off and one call will be stopped.

(Effects of the Invention) As described above, the present invention provides a power supply circuit that supplies power from a commercial power source, a power failure detection circuit that detects a power outage of the commercial power source, and a connecting means that connects and disconnects a telephone line. , switching means for controlling the closing means to keep the telephone line closed when the power failure detection circuit detects a power outage of the commercial power supply while the closing means is closing the telephone line; By keeping the TTT communication line closed for a certain period of time even if there is a power outage during a call, it is possible to continue talking using a telephone that operates only on the power supplied from the attached telephone line, which has practical effects. There is something big about it.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a telephone terminal device according to an embodiment of the present invention, FIG. 2 is a connection diagram of the telephone terminal device, FIG. 3 is a diagram showing voltage waveforms of a telephone line, FIGS. FIG. 5 is a diagram showing a line interface circuit of a conventional telephone terminal device. 23... Constant voltage regulator circuit, 24... Power failure detection circuit, 30... Photo coupler 32... Incoming call circuit, 33... Photo coupler for incoming call control 1.37...
・Incoming call detection circuit for attached telephone.

Claims (3)

[Claims] (1) A power supply circuit that supplies power from a commercial power source, a power outage detection circuit that detects a power outage of the commercial power source, a closing means that connects and disconnects a telephone line, and the closing means that closes the telephone line. and switching means for controlling the closing means to maintain the closed state of the telephone line when the power failure detection circuit detects a power failure of the commercial power supply while the telephone line is connected. . (2) While the closing means maintains the closed state of the telephone line, if the attached telephone off-hook detection circuit detects off-hook of the telephone attached to the telephone line, and the attached telephone off-hook detection circuit detects the off-hook of the attached telephone, the closing means is closed. 2. The telephone terminal device according to claim 1, wherein the switching means controls the switching means to open the telephone line. (3) A timer circuit that measures a certain time while the closing means maintains the telephone line closed, and controls the switching means so that the closing means opens the telephone line after a certain period of time. Claim (1) characterized in that
Telephone terminal equipment as described.