JPS5855716Y2 - Signal transmission/reception circuit in button telephone device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal transmission/reception circuit between a main device and a button telephone in a button telephone device.

Conventionally, this type of circuit is shown in Fig. 1, where 1 is a main device, 2 is a button telephone, 3 is a signal transmission circuit from the main device to the button telephone, and 4 is a signal transmission circuit from the button telephone to the main device. The signal transmission circuit includes pulse transmitting circuits 5 and 12, pulse transformers 6, 8, 9, and 11, and pulse receiving circuits 7 and 10 at both ends of each of the two lines.

According to this device, four wires are used for the cable between the main device and the key telephone, but if the other two wires necessary for audio frequency transmission are added, the number of cable cores becomes six, and the existing 4-wire cable cannot be used.

Further, the circuit shown in FIG. 1 has the disadvantage that it requires a large number of parts such as a pulse transformer and terminals, and is expensive.

The present invention overcomes the drawbacks of the conventional circuits mentioned above.

Hereinafter, the present invention will be explained with reference to FIG. 2, which is an example of implementing the present invention in a main device and a button telephone in a key telephone device.

In FIG. 2, 1 is a pulse transmitting/receiving circuit in the main device, 2 is a pulse transmitting/receiving circuit in a button telephone, 3 is a two-wire wire connected between the main device and the button telephone, and 4 and 17 are pulses having three windings. It's trance.

The main device transistor 7 has its collector connected to the second winding 6 of the pulse transformer as a load, and has an input terminal 8.
It constitutes the amplification/drive circuit for the pulse signal that is manually input.

Button telephone transistor 20. Winding 19. The input terminal 21 is also an amplification/drive circuit.

Third winding 16 of the pulse transformer of the main unit. resistance 11,
and 15. The diode 14 is a detection and amplification circuit for the received pulses from the line 3.

Button telephone transistor 28. Resistance 24. and 26,
Similarly, the diode 27 is a receiving pulse detection/amplification circuit.

Next, the operation of the embodiment of the present invention will be explained.

In FIG. 2, when transmitting a pulse signal from the main device to the button telephone, when a positive pulse with a width of 1 μs is applied to the input terminal 8, the base-emitter current of the transistor 7 flows for about 1 μs. A pulse current flows through the second winding 6 of the pulse transformer 4 serving as the collector load for about 1 μs, and the pulse current flows through the third winding 16 and the first winding 9.
A pulse current flows for approximately 1 μs depending on the terminal impedance of each terminal.

The first winding 9 of the main device is connected to the first winding 2 of the pulse transformer of the button telephone via two wires 3 with a maximum length of 500 m.
2, and each winding of the pulse transformer is related in direction as shown in the figure, so that when a pulse current flows to winding 6, it flows from winding 25 through resistor 26 to the base-emitter of transistor 28. A pulse current is generated, and the output terminal 29 becomes a low voltage while the pulse current is flowing, indicating that a pulse signal has been received.

At this time, a voltage is applied to the winding 19 with a polarity that increases the collector voltage to the collector of the transistor 20. However, since the input terminal 21 maintains the base-emitter of the transistor 20 in a reverse bias state by an external circuit, the winding line 19
No pulse current flows.

In Fig. 2, when transmitting a pulse signal from the key telephone to the main device, the input terminal 21 of the key telephone is
The same operation as described above is performed by inputting a positive pulse of seconds.

In FIG. 2, since the cable connecting the main device and the button telephone is long, there is a risk of an erroneous signal if external noise is induced into the 2nd wire 3. However, the noise pulse generated in the winding 25 is transmitted to the transistor 28 is ignored until a predetermined threshold voltage is reached and is therefore sufficiently distinguished from signal pulses.

In FIG. 2, diode 27 is necessary for protection of transistor 28, but by inserting resistor 26 in series with winding 25, the output pulse from winding 19 is not short-circuited and is properly It is guaranteed that the signal will be sent to line 3 at the output level.

In FIG. 2, the first winding of the pulse transformer is provided with mid-point taps 10 and 23 for transmitting power and audio frequency signals between the main device and the button telephone device using the mid-point taps. It is also possible to form lines.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional signal transmission/reception circuit between a main device and a button telephone, and FIG. 2 is a circuit diagram showing an embodiment of a signal transmission/reception circuit between a main device and a button telephone according to the present invention. In the figure, 1 is a pulse transmitting/receiving circuit in the main device, 2 is a pulse transmitting/receiving circuit in a button telephone, 3 is a 2-wire connected between the main device and the button telephone, 4 and 17 are pulse transformers having 3 windings, 7 , 13.20 and 28 are transistors, 11.15.24 and 26 are resistors, and 14.27 is a diode.

Claims (1)

[Scope of utility model registration request] In the button telephone device, a pulse transformer having three windings is provided at both ends of two wires connected between the main device and the button telephone, and the first winding of each pulse transformer is connected to the two wires.
a second winding connected to the collector of the first transistor, and a third winding connected to the base of the second transistor via a resistor so as to have opposite polarity to the base. A signal transmitting/receiving circuit for a button telephone device, characterized in that a diode is connected in parallel between the base and emitter of the second transistor.