JP2502506B2 - Network control circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network control circuit for connecting a facsimile machine to a line and automatically making and receiving calls.

2. Description of the Related Art FIG. 2 is a block diagram showing an example of a conventional network control circuit.

In this network control circuit, both the CML relay 201 and the S relay 205 are open and the relay 209 serially connected to the telephone network incoming detection circuit 210 is closed during standby. In this state, the line is connected to the telephone and the telephone network incoming detection circuit 210. A hookup detection circuit 250 including a varistor 211, a resistor 212, and a photocoupler 213 is connected in series with the telephone in order to detect the hook state of the telephone.

 This network control circuit operates as follows.

When there is an incoming call from the line, the facsimile machine detects a calling signal by the telephone network incoming detection circuit 210. And CML
Relay 201 is closed, the line and the modem are connected via hybrid transformer 204, and facsimile communication is performed. In this case, the DC loop for holding the line is formed by the letter coil 202, and the DC blocking capacitor 203 prevents the DC current from flowing to the hybrid transformer 204.

On the other hand, when making an automatic call, it is first confirmed that neither of the two photocouplers 213 of the hookup detection circuit 250 is emitting light, so that the hookup state is not established. Then, in order to prevent the collision with the incoming call, the relay 206 is closed, and it is confirmed by the photocoupler 208 that the polarity of the line is not reversed for a certain period of time. If the polarity of the line is not reversed for a certain period of time, the relay 206 is opened and the S relay 205 is closed. In this case, the line is held by the DC loop formed by the matching transformer 219 (corresponding to a hookup state in the telephone). Then, the dial pulse generation circuit 214 or the dial tone generation circuit 218 sends a dial signal to the line, and the relay 215 is closed.
Then, it waits for the photocoupler 217 to operate by reversing the polarity of the line in response to the partner. When the photocoupler 217 operates, it is considered that the other party responded, and the CML relay 201 is closed, the relay 215 and the S relay 205 are opened, and the modem is connected to the line. Then, facsimile communication is performed while this line is held by the DC loop formed by the letter coil 202. When communication is completed,
The CML relay 201 is opened, the line is connected to the telephone, the DC loop is broken if the telephone is not hooked up, and the line returns to the standby state.

However, such a conventional network control circuit has many components such as a relay, a transformer, and a coil, and it is inevitable that the network control circuit becomes large in size and expensive, and the control thereof becomes complicated. There was a problem.

The above problem occurs for the following reasons. First, a large number of sensors using photocouplers are required for the facsimile apparatus to detect the hook state and line state of the telephone. Secondly, due to the reliability of the relay contacts, the relay generating the dial pulse must be arranged independently of the telephone or modem circuit. Along with this, an S relay 205 for switching between the dial pulse generating circuit and the telephone circuit and a matching transformer 219 for connecting the line with the dial tone generating circuit 218 are required. Thirdly, in the circuit for detecting the polarity of the line (the resistor 207 and the photocoupler 208, the resistor 216 and the photocoupler 217), the line cannot be always connected to the line because of the reliability of the photocoupler. Relays 206 and 215 are needed to disconnect the line when not needed. As described above, in the conventional configuration, the ratio of expensive parts such as relays, transformers, coils, etc. is large, the cost of the entire circuit is high, and the size is increased.

The present invention has been made in view of the above problems, and is an expensive component such as a relay of a circuit polarity detection circuit, a dial pulse generation relay, a transformer and a letter coil for coupling a line and a dial tone generation circuit. It is an object of the present invention to provide a network control circuit having an automatic call-out function, which can minimize circuit size, facilitate control, and reduce cost.

Means for Solving the Problems In order to achieve the above object, the present invention is to detect a hook state of a telephone in a standby state, and a detecting means having photocoupler circuits connected in parallel in opposite directions and connected in series to a line. , A rectifier circuit connected to the detecting means for holding the polarity state of the line constant, and a line connected from the telephone side to the facsimile side at the time of receiving a call from the telephone network and making a call to the telephone network. Connection means for switching connection,
A first constant current circuit connected to the line so as to hold the line under the control of the facsimile when receiving a call from the telephone network, and to monitor the presence or absence of polarity reversal of the line when calling to the telephone network. A second constant current circuit having a set value smaller than that of the first constant current circuit connected in line,
The first constant current circuit operates as dial pulse generating means in accordance with on / off control from the facsimile when a call is made to the telephone network.

Operation With the above configuration, when a call is received, the line is held by the first constant current circuit when the device is connected to the facsimile and a DC loop is formed.

In addition, since a second constant current circuit having a set value smaller than that of the first constant current circuit is provided for making a call, it is possible to detect whether or not the polarity of the line is reversed by monitoring the state of the photocoupler circuit. it can.

Further, when automatic calling is performed, the first constant current circuit can generate a dial pulse in accordance with on / off control from the facsimile.

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

This network control circuit consists of a detection circuit 150 connected in series with the line.
And a rectifier circuit 104 that is connected in series to the detection circuit 150 and is configured with a diode bridge that converts the signal form from a balanced type to an unbalanced type while keeping the polarity state of the line constant, and on the output side of this rectifier circuit 104. A CML relay 105 as a means for connecting and connecting the facsimile circuit and the telephone circuit to the line, a constant current circuit 120 connected in parallel with the facsimile circuit, and a DC blocking capacitor 108 for the constant current circuit 120.
A dial tone generation circuit 111 for connecting between the modem and the hybrid transformer 109, which is connected via a telephone line and converted into a two-line-four-line configuration and connected to the modem, and for selecting a communication partner for the line. And a mixing circuit (MIX) 110 for switching or mixing the facsimile signal from the modem and the dial tone from the dial tone generating circuit 111.

The detection circuit 150 includes a photocoupler 101 connected in parallel to each other in the opposite direction and connected in parallel to a line, a resistor 103 connected in series to the photocoupler 101 and limiting a current flowing through the photocoupler 101, and a resistor connected to the photocoupler 101. And a varistor 102 that is connected in parallel to the device 103 and keeps the voltage applied to the photocoupler 101 constant.

The constant current circuit 120 sets the current flowing through the line to a large current (DC loop current), and the constant current circuit 10 is controlled to be turned on / off by the control unit of the facsimile so as to hold the line.
6 and a constant current circuit 107 connected to the line to monitor whether or not the polarity of the line is reversed by setting the current flowing in the line to a small current.
It has and. These constant current circuits 106 and 107 are composed of, for example, well-known emitter followers.
The emitter follower 106 has a value such that the resistance connected to the emitter side is small and the constant constant current circuit 107 is large so that the magnitude of the current can be set.

A telephone network incoming detection circuit 112 for detecting a call signal from the telephone network is connected in parallel with the telephone circuit connected to the CML relay 105.

Regarding the operation of the network control circuit configured as described above,
This will be described below.

During standby, the CML relay 105 is open and the line is connected to the telephone circuit via the detection circuit 150 and the rectification circuit 104. In this state, the telephone network incoming detection circuit 112 monitors the ringing signal due to an incoming call, and the detection circuit 150 monitors the telephone hook state.

When there is an incoming call from the line, the telephone network incoming detection circuit 112 detects the incoming call and closes the CML relay 105. At the same time, when the base voltage of the emitter follower in the constant current circuit 106 is turned on, a resistance circuit corresponding to a direct current loop is formed, so that the line is held. The facsimile signal from the line is guided to the modem through the detection circuit 150, the rectification circuit 104, the CML relay 105, the DC blocking capacitor 108, and the hybrid transformer 109. When sending the facsimile signal to the line, the mixing circuit 110 is controlled so as to pass the facsimile signal from the modem, and the facsimile signal is guided to the line in the opposite direction to the above by way of each component. Get burned.

When making an automatic call, the photo coupler 101 does not emit light, and after confirming that the photo coupler 101 is not in the hookup state, the call operation is started. First, the CML relay 105 is closed. Then
A constant current circuit 107 forms a resistance circuit between the constant current circuit 107 and GND, a small current flows into the photocoupler 101, and the polarity of the line is detected. If there is no polarity reversal of the line for a certain period of time, the constant current circuit 106 is turned on to hold the line and send the dial signal. When the dial signal is a dial pulse, the dial pulse is generated by turning on / off the base voltage of the emitter follower in the constant current circuit 106. When the dial signal is a dial tone, the dial tone generation circuit 111 generates a dial tone, and this dial tone is mixed circuit 110, hybrid transformer 109, DC blocking capacitor 108, CML relay 105, rectifier circuit 104, detection circuit.
Send to the line via 150. When the transmission of the dial signal is completed, the photocoupler 101 monitors that the polarity of the line is inverted by the response from the other party. Photo coupler 101
When is operated, it is considered that the other party responded, and the facsimile communication is started. When the facsimile communication is completed, the constant current circuit 106 is turned off. At the same time, the CML relay 105 is opened. This breaks the DC loop and returns the line to standby if the phone is not hooked up.

Effect of the Invention The polarity detection of the line and the hookup detection of the telephone are performed by the detection circuit having the photocouplers connected in parallel to each other, and the two constant current circuits having different set values are provided, which is necessary for the polarity detection. It becomes possible to pass a small current and a large current required for holding the line. Therefore, the use of parts such as relays, transformers, and coils required to monitor the line status required for network control and to turn on / off the DC loop current for network control is suppressed, and the size and cost are reduced. Therefore, the control can be facilitated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a network control circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional network control circuit. 101 …… Photo coupler, 105 …… CML relay, 106, 107, 1
20: constant current circuit, 150: detection circuit

Front page continuation (72) Inventor Takushi Iga 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Transmission Co., Ltd. (72) Inventor Takahiro Kikuchi 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsu Shimo Denshi Co., Ltd. (72) Inventor Toshio Narishima 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Denshi Co., Ltd. (72) Toshiaki Shinano 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsu Shimoden Co., Ltd.

Claims (1)

(57) [Claims] 1. A detection means for monitoring a hooked state of a telephone during standby and having photocoupler circuits connected in parallel in opposite directions and connected in series to a line, and a polarity state of a line connected to the detection means is constant. A rectifier circuit that holds the
By connecting means connected to the rectifier circuit to switch and connect the line from the telephone side to the facsimile side when receiving a call from the telephone network and when making a call to the telephone network, and by controlling the facsimile when receiving a call from the telephone network. A first constant current circuit connected so as to hold the line, and a first constant current circuit connected so as to monitor the presence / absence of polarity reversal of the line when a call is made to the telephone network. And a second constant current circuit having a set value, wherein the first constant current circuit operates as dial pulse generating means in accordance with on / off control from the facsimile when a call is made to the telephone network. Characteristic network control circuit.