JPS60196019A - Switching system of transmitting and receiving circuit - Google Patents

Abstract

PURPOSE:To attain the selective connection of an optional transmitting/receiving circuit to a circuit by putting a group of gates between a transmission/reception driver and each of plural transmitting/receiving circuits and controlling these gates. CONSTITUTION:A circuit driver 2, a circuit receiver 3, a transmission gate 4 and reception gates 5 and 6 are provided between a transmission/reception control part 1 and a transmitting/receiving circuit. A holding circuit 7 is set by the transmission signal of the part 1 and reset when no transmission signal is applied for a fixed period of time. The gate 6 is closed by the output of the circuit 7 and therefore the transmission signal is not sent back to a reception terminal RD. The gates 4 and 5 are opened by a switching indication signal A given from a switch control part 8. Thus the transmission signal is sent to a circuit. While the reception signal is received by the receiver 3 via gates 5 and 6. The same procedure is carried out also with another transmission/reception control part 1'. In such a way, a transmitting/receiving circuit is switched by delivering a signal A or B through the part 8 and at the logic level of each gate.

Description

TECHNICAL FIELD The present invention relates to a transmitting/receiving circuit switching system for switching and connecting a plurality of sets of transmitting/receiving circuits to one line.

BACKGROUND OF THE INVENTION FIG. 1 is a block diagram showing an example of a conventional transmitting/receiving circuit switching system. That is, the transmission signals of one set of transmission/reception circuits are output from the signal output terminal SD of the transmission/reception control section 1 and input to the line driver 2, and the line driver 2 converts the transmission signals to line level signals and outputs them. The output of the line driver 2 is the input signal from the 0 line connected to one of the switching contacts r of the switching relay L.
The output of the line receiver 3 is inputted to the signal receiving terminal RD of the transmitting/receiving control section l. Similarly to the above, the output of the line driver 2 connected to the signal output terminal SD of the other transmission/reception control section 1' is connected to the other switching contact of the relay L. By operating the relay L, any transmission/reception control unit l or 1' can be switched and connected to the line via the line driver 2 and line receiver 3.

Since the above-mentioned conventional system uses relays for switching, it has the disadvantage that a large number of relays are required for switching when there are a large number of transmitter/receiver circuits, resulting in high costs. Moreover, when the number of switching is small, an insulating film is formed on the surface of the relay contact, resulting in poor contact and a disadvantage that a complete connection is not established. Further, a relay driver is required to operate the relay L in response to a control instruction signal at a logic level, and there is a drawback that a special peripheral circuit is required.

In place of the contact r of the relay L, it is possible to use a switching element based on an electronic circuit, or a high-power switching element must be used that can turn on and off line-level signals. Further, in this case, it is necessary to pass both a high level transmitting signal and a low level receiving signal without any problem, and it is also necessary to be able to transmit a balanced bidirectional signal, which is not easy.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional drawbacks by inserting a group of cables operating at a logic level between a transmitter/receiver driver and each transmitter/receiver circuit, and to control the gate group by a control signal. It is an object of the present invention to provide a transmitting/receiving circuit switching system that allows selective connection of any transmitting/receiving circuit to a line by controlling the transmission/receiving circuit.

Structure of the Invention The transmitting/receiving circuit 9 switching method of the present invention is a transmitting/receiving circuit switching method in which any one of a plurality of sets of transmitting/receiving circuits is switched and connected to one line, and a transmission level signal is sent to the line. a line receiver for converting a line-level signal manually inputted from the line into a logic-level signal; and any one of the plurality of sets of transmitting/receiving circuits.
a first receiving gate for inhibiting human power on the receiving side while transmitting signals on the transmitting side of each of the transmitting/receiving circuits; a holding circuit that holds the first receiving gate while the side signal is being advanced, a transmitting gate that inputs the transmitting side signal to the line driver in accordance with the pJ instruction signal, and switching the output of the line receiver. and a second receiving gate that inputs the input signal to the first receiving cable in response to an instruction signal, and switches and connects one set of transmitter and receiver circuits to the line in accordance with the switching instruction signal outputted from the switching control section. It is characterized by connecting.

Embodiments of the Invention Next, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention.

That is, the signal output terminal f'SD of the transmission/reception control unit 1 is connected to the human power of the line driver 2 via the transmission cable 4,
The output of line driver 2 is connected to the line. The input of the line receiver 3 is connected to the connection between the output of the line driver 2 and the line, and the output of the line receiver 3 is sent to the transmission/reception control unit l via the second reception gate 5 and the first reception gate 6. Connect to receiving terminal RD. The holding circuit 7 is a transmission/reception control section l.
It is set by the transmission signal output from the signal output terminal SD of the device, is held for a certain period of time, and is set for a certain period of time. It is reset when there is no transmitted signal. The first receiving gate 6 is a gate that is closed by the output of the holding circuit 7. Therefore, during transmission, the first
Since the reception gate 6 is closed, the transmission signal is prevented from being input to the signal reception terminal RD of the transmission/reception control unit 1 via the line driver 2 and the line register/decoder 3. The transmitting gate 4 and the second receiving gate 5 are controlled by a cut-off control section 8.
When the transmitting gate 4 and the second receiving gate 5 are opened, the transmitting signal outputted from the signal output terminal SD of the transmitting/receiving controller l is Line driver 2 through gate 4
The signal is input to the line driver/controller 2, where it is converted into a line level signal and sent out to the line. Further, the signal received from the line is converted into a logic level signal by the line receiver 3, and is sent to the second receiving gate 5 and the first receiving gate 6.
The signal is input to the signal receiving terminal RD of the transmission/reception control unit l through the. That is, the transmission/reception circuit of the transmission/reception control section 1 is connected to the line via the line driver 2 and line receiver 3.

The signal output terminal SD of the other transmission/reception control section 1' is also connected to the line driver 2 via the same transmission gate 4' as above, and the output of the line receiver 3 is connected to the second reception gate 5'.
and the transmission/reception control section 1' via the first reception gate 6'.
is connected to the signal receiving terminal HD of. The above transmission gate 4'
The second reception gate 5' is a gate that is opened by the switching instruction signal B supplied from the switching control section 8. Therefore, when the switching instruction signal B is supplied from the switching control section 8, the transmission/reception circuit of the transmission/reception control section 1' is connected to the line. That is, the switching control unit 8 receives the DJ switching instruction signal A.
, H, the transmitting/receiving circuits are switched and connected by outputting any one of them. This switching operation is performed by transmitting gate 4. Since this is performed by logic level operations such as the second receiving gate 5, there are no mechanical operating parts like conventional relays, and the structure is simple and inexpensive.

In addition, there is no risk of contact failure of relay contacts.
Improved reliability. Furthermore, even when there are multiple sets of transmitting/receiving circuits, a gate group similar to the above may be inserted into each transmitting/receiving circuit, and each gate group may be opened or closed by a switching command signal outputted from the switching control section 8.

Effects of the Invention As described above, in the present invention, switching of a plurality of sets of transmitting/receiving circuits is performed using a switching command signal from a logic level gate circuit interposed between each transmitting/receiving unit and the line driver 4421 line receiver 3. Since the relay is configured to open and close by opening and closing, connection failures due to poor contact of relay contacts can be prevented and reliability can be improved. Furthermore, it does not use any mechanical parts, has a simple structure, can be provided at low cost, and can easily switch between multiple sets of transmitter/receiver circuits. In addition, the present invention
It can be easily constructed by simply adding a gate group to a conventional circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional transmitting/receiving circuit switching system, and FIG. 2 is a block diagram showing an embodiment of the present invention. In the figure, 1.1': transmission/reception control unit, 22 line triver, 3: line receiver, 4.4': transmission gate, 5.5
': second receiving gate, 6,6': first receiving gate,
7: Holding circuit, 8: Switching control section. Applicant: NEC Corporation Agent: Patent Attorney: Toshimune Sumita Figure 1

Claims (1)

[Claims] In a transmitting/receiving circuit switching method in which any one of a plurality of sets of transmitting/receiving circuits is switched and connected to one line, there is provided a line driver for sending a transmission level signal to the line, and a line level signal input from the line. a line receiver that converts the signal into a logic level signal, a switching control unit that outputs a switching instruction signal to connect any one of the plurality of sets of transmitting/receiving circuits to the line, and a transmitting side of each of the transmitting/receiving circuits. a receiving gate of 1s1 for prohibiting input from the receiving side while the signal is being transmitted; a holding circuit that is a signal output terminal of the transmitting side and closes the first receiving gate; A switching instruction signal output from the switching control unit, comprising a transmission gate for inputting to the line driver, and a second reception gate for inputting the output of the line receiver to the first reception gate according to the switching instruction signal. A transmitting/receiving circuit switching method characterized in that an arbitrary set of transmitting/receiving circuits is switched and connected to a line by using.