JPH0522423B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a data exchange system for mutually exchanging data between a plurality of data terminal devices.
The present invention relates to a call/disconnection signal transmission device for transmitting a call/disconnection signal.

[Prior art]

Conventional call/disconnection signals were transmitted by the method shown in FIG. FIG. 1a represents the original data (in bit series form), and FIG. 1b represents the transmitted data including call/disconnect signals. The original data is
As shown in D ₁₁ to _{D 61} , D ₁₂ to _{D 62} , and D ₁₃ to _{D 63} in FIG. An F bit (synchronization bit) is placed in front of the data, and an S bit (control bit) is placed after each 6-bit unit, and the data is transmitted so as to be wrapped in the F bit and S bit. The 8 bits from the F bit to the S bit are called one envelope, and this method is called the envelope method.

The S bit, which is a control bit, is used as a call/disconnection signal; when a call is made, the logic of the S bit changes from "0" to "1", and when a call is disconnected, the logic of the S bit changes from "1" to "0". do. In addition, the F bit is used for envelope synchronization, and repeats the logic of "1" and "0" for each envelope, so that such repeating bit patterns do not occur in the data bits and S bits. Therefore, by detecting this repeated bit pattern, the position of the F bit can be detected, and since the bit period is known, the positions of other bits in the envelope can be determined.

Conventionally, call origination and disconnection signals were sent using the method described above, so when transmitting 6 bits of data, the F bit and S bit were added, resulting in a total of 8 bits being transmitted. It is necessary to increase the transmission speed on the road by 8/6 times, and speed conversion in between,
The disadvantage is that the circuit configuration becomes complicated due to the detection of the F bit.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above. In this invention, a high frequency pulse having a repetition frequency higher than the bit timing signal of the data signal is used as a calling/disconnecting signal, and when the disconnection state is On the receiving side, the above-mentioned high-frequency pulse is transmitted, and in the calling state, the transmission of this high-frequency pulse is stopped and data is transmitted.The receiving side measures the interval between the logic change points of the received signal. This method detects the presence or absence of a pulse, thereby eliminating the need for speed conversion between data speed and transmission speed as in the conventional envelope method.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a time chart for explaining the signal configuration of the present invention, in which FIG. 2a shows the transmission data to be transmitted, FIG. The figure d shows the combination of the transmitted data and the call/disconnect signal, and the figure e shows the detection of the call/disconnect signal. There is.

FIG. 3 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a data terminal device, 2 is a data exchange, and 3 is a subscriber line. Both the data terminal device 1 and the data exchange 2 are subscriber lines. Only the third side is shown. 11 is a transmission data input terminal, 12 is an AND gate, 13 is a line driver, 14 is a NAND gate, 15 is a high frequency pulse generator, 16 is a call/disconnect switch, 21 is a line receiver, 22
is a received data output terminal, 23 is a signal detection circuit, 2
4 is a differential circuit, 25 is a D flip-flop, 26
2 is a pulse extinction monitoring circuit, and 27 is an OR gate.

The operation of the apparatus shown in FIG. 3 will be explained below. The transmission data of the data terminal device 1 (Fig. 2 a) is shown in Fig. 2 b.
The signal is input from terminal 11 to one input terminal of AND gate 12 at the bit timing of . The output of the NAND gate 14 is connected to the other terminal of the AND gate 12, but when a call is made, the switch 16 is connected to the ground side (logic "0"), so the output of the NAND gate 14 becomes "1". , the transmission data input is output to the subscriber line 3 via the line driver 13 as is.

In the data exchange 2, the signal on the subscriber line 3 is received by the line receiver 21, and the received data output terminal 2
Output to 2. When there is no transmit data input,
The signal logic of terminal 11 is kept at "1". The signal detection circuit 23 detects the signal input from its terminal T.
For example, it is composed of a counter that counts rising points, and is configured to input a logic "1" signal to the D terminal of the D flip-flop 25 when the counted value of this counter exceeds a predetermined value. The differentiating circuit 24 inputs a transmission speed timing pulse having a frequency equal to the bit timing pulse (FIG. 2b) of the transmission data, and resets the counter constituting the signal detection circuit 23 with the pulse at its rising point, for example. Since the interval between the rising points of the data signal is greater than the interval between the transmission rate timing pulses, the signal detection circuit 23 is always in a reset state.

When the switch 16 is connected to the +5V side (logic "1" side), the output of the high frequency pulse generator 15 passes through the NAND gate 14, and while the signal logic at the terminal 11 is "1", it passes through the AND gate 12. The signal is output to the terminal 22 via the line driver 13, the subscriber line 3, and the line receiver 21, and at the same time is input to the signal detection circuit 23. The high frequency pulse has a higher frequency than the transmission speed timing pulse, and the transmission speed timing pulse causes the signal detection circuit 2 to
3 is reset, the output point of the D flip-flop 25 becomes a logic indicating a disconnected state because it is designed so that the logic at its output point becomes "1". When the switch 16 is connected to the ground side, the high frequency pulse is no longer sent out, and the signal detection circuit 23 is reset at the rising point of the next transmission speed timing pulse, and the D flip-flop 25 is reset.
The output of is a logic indicating the calling status. In this way, the call origination and disconnection states can be detected by the output of the flip-flop 25, and the signal detection circuit 23 is reset by the transmission speed timing pulse with the same frequency as the bit timing pulse, so that synchronization is not performed as in the conventional envelope method. Transmission that does not require bits or control bits becomes possible.

Symbol S in the block of D flip-flop 25
At the set input terminal, the D flip-flop 25 is initialized by setting the D flip-flop 25 to the logic representing the disconnected state via an OR gate using the output of the pulse extinction monitoring circuit 26 and a signal at the time of power supply reset. The pulse disappearance monitoring circuit 26 outputs a signal to set the D flip-flop 25 when there is no input of transmission data or high frequency pulse for a predetermined period of time.

In the above embodiment, the case where the call origination/disconnection signal is sent from the data terminal device 1 side to the data exchange 2 side has been described, but it can also be applied to the case where the disconnection signal is sent from the data exchange side. is clear. Further, in the apparatus of the present invention, since either the transmission data signal or the high frequency pulse is constantly sent to the subscriber line, line abnormalities can be easily detected by the pulse extinction monitoring circuit.

〔Effect of the invention〕

As described above, according to the present invention, a pulse wave with a repetition frequency sufficiently higher than the data transmission rate is used for the call/disconnection signal, so there is no need for speed conversion between the data rate and the transmission rate. This has the effect of eliminating the need to add synchronization bits and control bits.

[Brief explanation of drawings]

FIG. 1 is a format diagram showing a conventional method, FIG. 2 is a time chart for explaining the signal structure of the present invention, and FIG. 3 is a block diagram showing an embodiment of the present invention. 1...Data terminal device, 2...Data exchanger,
3...Subscriber line, 15...High frequency pulse generator,
16...Call/disconnect switch, 23...Signal detection circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1 Call origination/disconnection signals for transmitting call origination/disconnection signals via subscriber lines between data terminal equipment and data exchange equipment when exchanging data in the form of digital codes.
The disconnect signal transmission device includes a high frequency pulse generator provided on the data transmitting side and having a higher repetition frequency than the bit timing pulse of the data signal, and a high frequency pulse generator provided on the transmitting side that generates the high frequency pulse in the disconnected state. a call originating/disconnecting switch that stops sending out the high frequency pulse when a calling signal is sent to the subscriber line; and a pulse that is provided on the data receiving side and is reset at the bit timing pulse period and is input from the subscriber line. a signal detection circuit that counts the period of time according to the bit timing pulse cycle and generates an output when the counted value is greater than or equal to a predetermined value;
A flip-flop generates a logic output indicating a calling state or a disconnected state depending on the presence or absence of the output of this signal detection circuit, and the flip-flop is disconnected when the receiving side does not receive the data signal and the high frequency pulse for a predetermined period of time. A transmission device for a call/disconnection signal, comprising a pulse extinction monitoring circuit that outputs a logic state.