JPH0342791Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a button telephone device, and more particularly to a signal transmission/reception circuit between a main device and a button telephone device.

[Conventional technology]

This type of signal transmitting/receiving circuit that has been used in the past is shown in FIGS. 3 and 4.

FIG. 3 shows an example in which separate pulse transformers are used for transmission and reception, where 1 is a signal line from the main device 100 to a button telephone (handset) 200, and 2 is a signal line between the key telephone 200.
Signal lines 101 and 20 from to the main device 100
1 are a main device 100 and a button telephone 2, respectively.
The pulse sending circuits 102 and 202 on the 00 side are also pulse receiving circuits, and 103, 104 and 203, 204 are pulse transformers.

On the other hand, Fig. 4 shows an example using a three-winding pulse transformer (publication of Utility Model Publication No. 58-55716), in which 11 is a signal line connecting the main device 100 and the button telephone 200, and 111 and 211 are three-winding pulse transformers. Transformer, 112, 212 is a transmitting transistor, 11
3,213 is a receiving transistor.

[Problem that the invention attempts to solve]

However, the configuration shown in Figure 3 not only requires a large number of parts such as pulse transformers, but also requires four wires just for signal transmission and reception, and six wires when adding the communication wire, making wiring difficult and expensive. There is a problem.

Further, in the case of the one shown in FIG. 4, the pulse transformer itself has a large number of windings and is not only expensive, but also has a large number of terminals, making it difficult to downsize. For example, in the case of a star connection, the main device requires pulse transformers for the number of button telephones, but if the pulse transformer is configured with a 16-pin dual in-line package, 6 pins are required for 3 windings, and 2 I can only take it. Therefore, a system with eight key telephones would require four packages.

[Means for solving problems]

In this invention, the direction of the winding of the pulse transformer, which terminates a pair of signal wires connecting the main device and the button telephone at the first winding, is changed to the second winding of the pulse transformer according to the transmitted pulse and the received pulse. Set the generated voltage to have opposite polarity, connect the base of the receiving transistor to one end of the second winding of the pulse transformer via a resistor, and connect the emitter of the receiving transistor to operate based on the transmitted pulse. The other end of the second winding of the pulse transformer is connected to the collector of a transmitting transistor and the anode of a diode, and the cathode of this diode is connected to the emitter of a receiving transistor.

[Effect]

During transmission, a pulse voltage is applied to the second winding side of the pulse transformer by turning on/off the transmission transistor, and the pulse voltage is sent to the signal line. On the receiving side, since they are connected with opposite polarity, a pulse voltage of opposite polarity is generated to turn on/off the receiving transistor.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, 21 is a pair of signal lines connecting the main device 100 and the button telephone 200;
Both ends are connected to pulse transformers T of the main device 100, respectively.
10 and the first winding of the pulse transformer T11 of the button telephone 200.

One end of the second winding of the pulse transformer T10 is connected to the base of the receiving transistor Q20 via a resistor R20, and the other end is connected to the collector of the transmitting transistor Q10. It is connected to the emitter of a receiving transistor Q20 via a diode D10. Similarly, one end of the second winding of the pulse transformer T11 is connected to the base of the receiving transistor Q21 via the resistor R21, and the other end is connected to the collector of the transmitting transistor Q11. The collector of is connected to the emitter of the receiving transistor Q21 via the diode D11.

The directions of the first and second windings of both pulse transformers T10 and T11 are set so that the voltages generated in the second windings are of opposite polarity due to the transmitted pulse and the received pulse, respectively, as shown in the figure. .

Next, the operation will be explained using FIG. 2.

First, when transmitting a signal from the main device 100 to the button telephone 200, the transmission pulse signal S0 is applied to the base of the transmission transistor Q10, thereby turning the transistor Q10 on/off as shown in FIG. 2d. At this time, since the second winding of the pulse transformer T10 is connected to the power supply (voltage Vcc) and the collector of the transistor Q10, a pulse voltage V _M is applied in synchronization with the transmission pulse signal as shown in Fig. 2e. f in the same figure, which occurred on the secondary side.
A voltage V _L as shown in is sent to the signal line 21.
At this time, the receiving transistor Q20 has a base current due to the emitter-base voltage drop of the diode D20 and the transistor Q20 itself.
i _B20 does not flow and does not work.

Since the windings of the pulse transformer T11 of the button telephone 200 are connected with opposite polarity, the pulse voltage V _L output to the signal line 21 is applied to the second winding side of the pulse transformer T11 as shown in FIG. 2g. produces a negative pulse voltage _VS. That is,
The data signal arriving at the primary side of the pulse transformer T11 shown in diagram f in FIG.
It comes to be guided to the secondary side of 1. In other words, in this case, the primary winding and the secondary winding are connected to have opposite polarities, and the diode D11 is connected in parallel to the secondary winding, so the pulse transformer T11 Transistor Q between the next windings
11 is off, a negative pulse voltage V _S as shown in diagram g is induced.

Therefore, when the pulse voltage V _S is negative (-), the pulse transformer T11
A potential difference is generated between the secondary windings of the transistor Q21, and at this time, the base current i _B21 flows from the transistor Q21 to the emitter of the transistor Q21 via the resistor R21, the secondary winding of the pulse transformer T11, and the diode D11, and the signal waveform is is as shown in Figure i. As a result, the receiving transistor Q21 is turned on/off as shown in FIG. By turning on/off the transistor Q1, a received pulse signal R1 as shown in FIG. 2k is obtained.

The same goes for transmitting a signal from the button telephone 200 to the main device 100. Transistor Q11 is turned on/off as shown in FIG. 2h by transmission pulse signal S1, and pulse voltage V _S is applied. On the other hand, a pulse voltage V _L of the opposite polarity is sent to the signal line 21, and a pulse voltage _VM of the opposite polarity to the pulse voltage _VS is generated in the pulse transformer T10 of the main device 100. As a result, a base current i _B20 as shown in FIG. 2c flows, turning on/off the receiving transistor Q20 as shown in FIG. 2b, and a reception pulse signal R0 as shown in FIG. 2a is obtained. .

Note that the diodes D20, D21 and their lines are connected to the receiving transistors Q20, Q2 during transmission.
This is to ensure that 1 does not operate.
May be omitted. In addition, diodes D10, D1
1 is inserted in pairs with these diodes D20 and D21, respectively. Note that R10, R11,
R30 and R31 are resistors.

The pulse transformers T10 and T11 are both two-winding transformers and have four terminals, so a 16-pin dual-in-line package can take four, and even a system with eight button telephones can be configured with two packages.

[Effect of idea]

As explained above, according to the present invention, the direction of the winding of the pulse transformer is set so that the voltage generated in the second winding due to transmitted and received pulses has the opposite polarity, and a resistor is connected to one end of the second winding. The base of the receiving transistor is connected through the terminal, the emitter of the receiving transistor is connected, the other end is connected to the collector of the transmitting transistor, and the collector of the transmitting transistor and the receiving emitter are connected through a diode. Therefore, a transmitter/receiver circuit can be constructed at low cost by using a two-winding pulse transformer, and furthermore, it can be made smaller because the number of terminals of the pulse transformer is small.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
The figure is a time chart to explain its operation,
FIGS. 3 and 4 are circuit diagrams showing conventional examples, respectively. 21...Signal line, 100...Main device, 200...
...Button telephone, Q10, Q11... Transmitting transistor, Q20, Q21... Receiving transistor, D10, D11... Diode, R20, R
21...Resistor, T10, T11...Pulse transformer.

Claims (1)

[Scope of utility model registration request] In a button telephone device in which at least one end of a pair of signal lines connecting the main device and the button telephone is terminated with the first winding of a pulse transformer, and signals are transmitted and received via the pulse transformer, the winding of the pulse transformer is Set the direction so that the voltage generated in the second winding of the pulse transformer is opposite in polarity between the transmitted pulse and the received pulse, and connect the base of the receiving transistor to one end of the second winding of the pulse transformer via a resistor. At the same time, connect the emitter of the receiving transistor, connect the collector of the transmitting transistor and the anode of the diode to the other end of the second winding of the pulse transformer, and connect the cathode of this diode to the emitter of the receiving transistor. A signal transmitting/receiving circuit for a button telephone device.