JPH0353830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a network control circuit for connecting a facsimile device having a communication function to a line.

Prior Art A conventional network control circuit of this type has a configuration as shown in Fig. 2, in which CML relay 1 is activated during standby.
is in an open state, and the line is connected to the telephone set, subscriber telephone network incoming call detecting means 2 and facsimile communication network incoming call detecting means 3, respectively. When an incoming call signal from the network is detected, the CML relay 1 is closed, and the telephone set, subscriber telephone network incoming call detection means 2, and facsimile communication network incoming call detection means 3 are disconnected from the line.

When the CML relay 1 is closed, the letter coil 4 forms a direct current circuit of the line, and the letter coil 4 is connected to the facsimile device via the hybrid coil 5 for two-wire and four-wire conversion by AC coupling using a capacitor from both ends thereof.

In the case of automatic call origination, it is necessary to prevent collision with an incoming call. For this purpose, the L relay 6 is first closed, and the output 8 of the photocoupler 7 is used to confirm that there is no polarity reversal of the line for a certain period of time before the incoming call. After confirming
The CML relay 1 is closed, the P relay 9 is turned on and off according to the number of the other party, and a pulse dial signal is transmitted to the network.

When all digits of the dial number have been sent, the polarity reversal detection circuit 10 confirms the other party's response, closes the CML relay 1, and performs facsimile communication with the line captured.

Note that the separator 11 is normally in a closed state except during testing or maintenance inspection. The subscriber telephone network incoming call detection means 2 and the line are coupled by a photocoupler which is AC-coupled by a capacitor, and the facsimile communication network incoming call detection unit 3 and the line are coupled by a transformer which is AC-coupled by a capacitor. It is being said. When the disconnector 11 is in the open state for testing or maintenance, the telephone is on standby or for a call due to a control procedure.
The line is connected when CML relay 1 is opened.
There is also a 2 similar to hybrid coil 5 inside the phone.
A four-wire conversion circuit is built-in, and the transmitter and receiver are connected to the line.

Problems to be Solved by the Invention However, the above-mentioned conventional network control circuit
Since the incoming call detection means 2 and 3 have a circuit configuration that is independent of the line, it is impossible to connect and use them with a modem circuit that has both functions of incoming call detection and communication. A problem arose.

The present invention was attempted in view of the above-mentioned problems, and an object of the present invention is to provide a network control circuit that can use a modem circuit that has both incoming call detection and communication functions.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is configured to switch the impedance of the line when detecting an incoming signal and during facsimile communication.

Effects With the above-described configuration, the present invention can maintain a high impedance with respect to the line when detecting an incoming signal, and switch the high impedance to maintain a predetermined impedance during facsimile communication. Therefore, the network control circuit according to the present invention can be connected to a modem circuit that has both the functions of incoming signal detection and facsimile communication.

Embodiment FIG. 1 is a schematic circuit diagram showing an embodiment of a network control circuit according to the present invention.

In FIG. 1, reference numeral 21 is a disconnector for disconnecting from the network control circuit and connecting directly to a test telephone (not shown) during testing or maintenance inspection, and this disconnector 21 is composed of a slide switch. has been done. Incidentally, normally, a test telephone is not required, and the disconnector 21 is kept in a closed state.

Reference numerals 22 and 23 are CML relays for switching between detecting an incoming signal and facsimile communication, and in the standby state, these CML relays 22 and 23 are in an open state.

24 and 25 are resistors for shunting the direct current of the line and supplying current to the light emitting diodes constituting the photocoupler 26. 27 is a varistor for overvoltage protection.

The photocoupler 26 is for detecting the presence or absence of polarity reversal of the line, and in this embodiment is composed of a pair of light emitting diodes and a transistor connected in parallel in opposite directions.

28 is a modem circuit (hereinafter referred to as an incoming call detection/communication circuit) that has both the function of detecting an incoming signal from the line and the function of performing facsimile communication using the line, 29 is a high impedance coupling coil, and 30 is a letter board. The coil 31 is a 2-wire/4-wire conversion hybrid coil, and 32 is a P relay.

Next, the operation of the network control circuit constructed as described above will be explained.

In the standby state, both CML relays 22 and 23 are open, and the incoming call is detected and transmitted to the line via the high-impedance coupling coil 29.
It is connected to the communication circuit 28, and the incoming call detection/communication circuit 28 is in the state of detecting an incoming signal. In this automatic call receiving operation from the standby state, when an incoming call signal from the network is detected by the incoming call detection/communication circuit 28 through the high impedance coupling coil 29, the CML relays 22 and 23 are closed, and the coupling coil 29 and Telephones are becoming disconnected from the line. When the CML relays 22 and 23 are closed, the letter coil 30 forms a DC circuit of the line, and the incoming call detection/communication circuit 28 is connected to the incoming call detection/communication circuit 28 via the hybrid coil 31 for 2-wire/4-wire conversion from both ends of the letter coil 30 with AC coupling by capacitors. is connected and communication is possible.

In the case of automatic call operation, it is necessary to prevent collision with an incoming call, and for this purpose, the output of the photocoupler 26 is first maintained for a certain period of time T ₁ (for example, approximately 300
milliseconds) to detect whether or not there is a polarity reversal on the line to prevent collisions between incoming and outgoing calls.

When the photocoupler 26 detects that the polarity of the line has reversed during the certain period of time _T1 , an incoming signal from the network is sent, and from then on, the same operation as when automatically receiving an incoming call is performed. .

In addition, the observation time T ₁ of the output of the photocoupler 26
If no line polarity reversal is detected within
The CML relays 22 and 23 are blocked, and the P relay 32 is turned on and off according to the other party's number to generate pulses.
Transmits the dial signal to the network.

When all digits of the dial number have been sent, the photocoupler 26 confirms the other party's response, and the CML relays 22 and 23 are closed to capture the line and perform facsimile communication via the incoming call detection/communication circuit 28.

When the photocoupler 26 does not detect a polarity reversal as a connection response confirmation from the network at the end of dialing, or when an interrupt instruction from the network is detected as a polarity reversal during facsimile communication, the photocoupler 26 returns to the above-mentioned standby state. .

Effects of the Invention In summary, the network control circuit of the present invention has a circuit configuration that includes a control means for switching impedance of a line, and therefore, this impedance switching control allows switching between standby state and facsimile communication. A switch is made. Therefore, in the past, the incoming call training means was provided independently from the modem circuit, so it was not possible to connect a modem circuit that had both incoming call detection and communication functions. This has the effect of making it possible to connect to the line of a modem circuit that has both the function of detecting incoming signals from the network and the function of communicating using the line.

[Brief explanation of drawings]

FIG. 1 is a schematic circuit diagram showing an embodiment of a network control circuit according to the present invention, and FIG. 2 is a schematic circuit diagram of a conventional network control circuit. 21...Disconnector, 22, 23...CML relay,
26...Photocoupler for line polarity reversal detection, 2
8...Modem circuit (incoming call detection/communication circuit), 29
...High impedance coupling coil, 30...Letter coil, 31...2-wire 4-wire conversion hybrid coil.

Claims (1)

[Claims] 1. A modem circuit having both the function of detecting an incoming signal from a line and the function of communicating using the line, and a first coil having a predetermined impedance provided between the modem circuit and the line;
a second coil having high impedance provided between the modem circuit and the line;
and a relay for switching connection between the coil and the second coil, the relay connects the second coil in a standby state, and the modem circuit detects an incoming signal through the second coil. A network control circuit characterized in that communication is sometimes performed by connecting the first coil using the relay.