JPS61135263A - Transmission system of control signal - Google Patents

Abstract

PURPOSE:To attain the use of a miniature pulse transformer in order to eliminate DC components and to prevent the deterioration in noise margin, by using a modulation circuit and a polarity inverting circuit. CONSTITUTION:When data on H is supplied to an input terminal 1 while a modulation signal is supplied to an input terminal 2, a modulated pulse train is supplied to one of two NAND circuits IC3 and 4. In this case, an output L emerges only on one of the circuits IC3 and 4 according to the state Q or Q' of a flip-flop IC2. The states Q and Q' are inverted for the IC2 with the fall of a pulse. Thus the IC3 or IC4 where the output L emerges is changed by the next pulse. A driver receiver circuit DR1 which drives the IC3 and 4 deliver H to T1 when I1 has the L input and then to T2 when I2 has the L input respectively. Then a pulse transformer PT1 is driven in both positive and negative polarities with a 1/2 frequency of a modulation signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control signal transmission system between a main device and a terminal or telephone in a button telephone device, EPBX, etc.

(Prior art) Conventional button telephone device 1. In the case of balanced transmission, control signals are transmitted directly between a main device such as an EPBX and a terminal or telephone using a transformer.

(Problem to be solved by the invention) However, when the bit width of the signal is long, or when the number of pits is large in NR and Z codes, the transformer used becomes large, and the performance deteriorates due to DC drift and the noise margin The disadvantage was that it decreased.

An object of the present invention is to provide a transmission system that can use a small pulse transformer, is inexpensive, has high performance, and has a large noise margin.

(Means for Solving the Problems) A feature of the present invention to achieve the above object is that in a control signal transmission system in which a control signal is sent to a line via a transformer, the control signal is modulated by a clock signal. After inverting the polarity of the output every clock and removing the DC component, it is sent to the line via the transformer, and on the receiving side, the received signal is double-wave detected and then passed through a low-pass filter to reproduce the control signal. It's in the signal transmission method.

(Function) With the above configuration, the control signal is modulated and sent to the line with its polarity alternately inverted. Therefore, even if the signal has a wide focus width or a large number of bits in NRZ, the transmitted signal will essentially be a high-frequency alternating current.
It can be sent to the line via a small transformer. There are no problems caused by DC drift. On the receiving side, after double-wave detection is performed on the received signal, a control signal is reproduced via a low-frequency F wave detector. Since the signal is a high-frequency alternating current, the transformer can be small, and an inexpensive transmission system with a large noise margin can be obtained.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which the input terminal 1 on the transmitting side is a data input terminal, and the AND circuit IC
Connected to one input of 1. Input terminal 2 is a modulation signal input terminal and is connected to the other input of AND circuit ICI. The output of the AND circuit IC1 is the NAND circuit IC3,
' It is connected to one input of IC4 and also to the clock input of flip-flop IC2. The output Q of the flip-flop IC2 is the other input of the NAND circuit IC3,
Q is connected to the other input of the NAND circuit IC4.

The outputs of the NAND circuits IC3, rc4 are connected to inputs I, , I2 of the driver/receiver circuits DR,1. DR, 1
The transformer side outputs T, , T2 are connected to the secondary side of the pulse transformer PTI, and the center of the secondary side is grounded.

The primary side of the pulse transformer PTI is a line output, and is connected to the primary side of the receiving side pulse transformer PT2 through a line. The pulse transformer PT2 and driver/receiver circuit DR,2 on the receiving side are connected in the same way as on the transmitting side. Receiving side driver/receiver circuit DR, T of 2
The TL standard output O is connected to a low-frequency r-wave generator consisting of a resistor R and a capacitor C, and the output of the r-wave generator is output to the output buffer 1B.
The signal is input to the μCPU (microprocessor) connected to terminal 3 on the receiving side.

First, when "H" data is input to input terminal 1 while a modulation signal is input to input terminal 2 (Fig. 20A),
The modulated pulse train is input to one input terminal of the NAND circuit IC3, IC4 (FIG. 20B), but the flip-flop I
Depending on the states of Q and Q of C2, only one of the NAND circuits IC3 and IC4 outputs "L". At the falling edge of the pulse, Q and Q of the NAND circuit IC2 are inverted, so the next pulse outputs "LI+" from the IC (IC3 or IC3).
4) changes. The driver Keshi-3 circuit DRI driven by the NAND circuit IC3 and IC4 outputs ・H・ to T1 when there is an ``Ln'' input to the circuit, and T2 when there is an ``L'' input to T2.
1H" is output. Therefore, the pulse transformer T.

is driven in both positive and negative polarities at the frequency 172 of the modulation signal (D in Figure 2).

The bipolar signal transmitted to the receiving side is
Both waves are rectified by receiver circuit 2 (E in Figure 2), and the low-frequency P
After the wave (FIG. 20F), the original data is reproduced through the buffer (FIG. 2G).

(Effects of the Invention) As explained above, this invention has the advantage of being able to use a small pulse transformer because it is equipped with a modulation circuit and a polarity reversal circuit, so it can remove the direct current component at low cost and prevent a reduction in noise margin. . Furthermore, since a low-frequency P-wave device is used, the influence of high-frequency noise can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing waveforms at various parts.

Claims (1)

[Claims] In a control signal transmission method that sends a control signal to the line via a transformer, the control signal is modulated with a clock signal,
After inverting the polarity of the modulated output every clock and removing the DC component, it is sent to the line via the transformer, and on the receiving side,
A control signal transmission method characterized by regenerating the control signal through a low-pass filter after double-wave detection of the received signal.