JPH0638523Y2 - Network control circuit - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application)
The present invention relates to a network control circuit (NCU circuit) having an incoming call collision prevention function and a line reverse detection function.

(Prior Art) A network control circuit in a data communication device or a facsimile connected to a telephone line together with a telephone is
It has two functions: a DC loop detection function for detecting whether or not the handset of the telephone is up, and an AC reception signal detection function for detecting whether or not a ringing AC signal (bell signal) has arrived.

Conventionally, as this type of network control circuit, there is one described in Japanese Patent Application Laid-Open No. 57-31256. The configuration will be described below with reference to the drawings.

FIG. 2 is a circuit diagram showing a configuration example of a conventional network control circuit.

This network control circuit shares a DC loop detection circuit for AC reception signal detection, and has a telephone line terminal 1 connected to a telephone line and a telephone terminal 2 connected to a telephone. 1 is switched and connected to a telephone terminal 2 or a communication terminal device 4 such as a facsimile by a relay contact 3. The phone terminal 2 has a paired photo coupler 5-
1 and 5-2 are connected in series, and an AND gate (hereinafter referred to as an AND gate) 6 that takes a logical product of the output states (OFF, OFF) of the photocouplers 5-1 and 5-2 is connected to the output side of the photocouplers 5-1 and 5-2. Has been done. The output side of the AND gate 6 is connected to the signal inverting inverter 7 and the setting time constant circuit 8-1. Further, the output side of the inverter 7 is connected to the setting time constant circuit 8-1. A time constant circuit 8-2 for resetting with different charge / discharge times is connected. Each time constant circuit 8-
1 and 8-2 each have a time constant of 100 ms or more,
No output occurs for pulses of ms or less.

On the output side of the time constant circuits 8-1 and 8-2, a set-reset type flip-flop (hereinafter referred to as "set-reset type flip-flop" that is set by one of the time constant circuits 8-1 and reset by the other time constant circuit 8-2 , RS-FF) 9 is connected, and the RS-FF
The reset output terminal of 9 is connected to the output terminal 10 for the DC loop detection signal Sd. Further, the set output terminal of RS-FF9 and the output side of the inverter 7 are connected to a 2-input AND gate 11, and the output side of the AND gate 11 is connected to the output terminal 12 for the detected AC reception signal Sa. ing.

Next, the operation will be described.

In a standby state in which the telephone handset is not up (on-hook state) and the ringing AC signal does not arrive at the telephone line terminal 1, the photocouplers 5-1 and 5-2 are off and off, and the AND gate 6 Output is at H level.
Since this H level charges the setting time constant circuit 8-1, the output of the circuit 8-1 becomes H level after a fixed time, and RS-FF9 is set. Then, the AND gate 11 is opened. In this state, when a call AC signal of 16 Hz (= 62.5 ms) arrives at the telephone line terminal 1, the photocouplers 5-1 and 5-2 are repeatedly turned on and off, and the AND gate 6 and the inverter 7 outputs H-level and L-level intermittent outputs are generated. At this time, charging of the reset time constant circuit 8-2 does not proceed, RS-FF9 maintains the set state, and the AND gate 11 is opened. Therefore, the intermittent output of the inverter 7 is in the form of the AC reception signal Sa. Output from the output terminal 12. The AC reception signal Sa is used for turning on the power of the device 4 and starting the reception operation.

On the other hand, when the handset of the telephone is lifted from the standby state (off-hook state), the telephone forms a DC loop, one of the photocouplers 5-1 and 5-2 is turned on, and the AND gate 6 is turned on. The output becomes L level, and the output of the inverter 7 becomes H level. This H level charges the reset time constant circuit 8-2, and the circuit 8-2 becomes H level after a certain period of time to reset RS-FF9. This reset output is output terminal 10 as DC loop detection signal Sd.
Is output from. At this time, the AND gate 11 is closed.

When dialing is performed by the telephone in this state, a transient signal similar to the arrival of the ringing AC signal is generated at the outputs of the photocouplers 5-1 and 5-2 due to the transient of the loop current. However, since it is an intermittent signal, charging of the set time constant circuit 8-1 does not proceed, and RS-FF9
Holds the reset state and closes the AND gate 11, so that the AC reception signal Sa is not output from the output terminal 12. As a result, it is possible to prevent the output of the regular AC reception signal Sa and the confusing pseudo AC signal.

(Problems to be Solved by the Invention) However, in the network control circuit having the above-mentioned configuration, a collision / incoming call collision preventing means for detecting that there is an incoming call and stopping the calling operation is provided. Moreover, there is a problem in that it is not functionally sufficient because the polarity reversal (reverse) of the line due to the response of the other party cannot be detected.

Therefore, in order to solve such a problem, Japanese Patent Laid-Open No.
It is possible to combine the ringing detection circuit described in Japanese Patent Laid-Open No. 112196 and the network control circuit described in Japanese Patent Laid-Open No. 58-219863, but there is a drawback that the circuit configuration is plural.

The present invention provides a network control circuit that solves the problems of the above-mentioned conventional technology, which is difficult to prevent call / call collision and to detect line reverse with a relatively simple circuit configuration. To do.

(Means for Solving Problems) In order to solve the above problems, the present invention is a network control which is connected between a line and a communication terminal device and switches connection of the line to the communication terminal device. In the circuit, a detection circuit that outputs two logic signals corresponding to the DC loop current of the line and the ringing AC signal, and a gate that outputs the two logic signals based on a dial mask signal by inputting the two logic signals And a first logic circuit for controlling. Further, the logical sum of the output terminal for outputting the two logic signals output from the first logic circuit to the mechanism capable of detecting the line reverse and the two logic signals output from the first logic circuit are calculated. There are provided a second logic circuit and a one-shot circuit having a time constant longer than the cycle of the calling AC signal and being drigged at the output of the second logic circuit.

(Operation) According to the present invention, since the network control circuit is configured as described above, the detection circuit outputs the detection signal according to the DC loop current and the ringing AC signal, and the one detection circuit outputs the one through the first and second logic circuits. Activate the shot circuit. The continuity of the ringing AC signal can be confirmed by the output of the one-shot circuit, and thus the incoming and outgoing call collision can be prevented. Here, the first logic circuit has a function of blocking the output of a regular AC reception signal and a confusing pseudo AC signal based on the dial mask signal, for example, during dialing of the telephone of the first logic circuit. Then, based on the output signal of the first logic circuit output from the output terminal, it is possible to detect the polarity inversion due to the partner response, that is, the reverse detection of the line. Therefore, the above problems can be eliminated.

(Embodiment) FIG. 1 is a circuit diagram of a network control circuit showing an embodiment of the present invention.

This network control circuit is connected to the telephone line and the calling AC signal Si
Has a telephone line terminal 20 for inputting and a telephone terminal 21 connected to a telephone, and the telephone line terminal 20 is connected by a contact 22 such as a relay or a switch to the telephone terminal 21 or a communication terminal device 23 such as a data terminal or a facsimile. It is switched and connected to. The telephone terminal 21 is connected in series with a detection circuit that outputs two logic signals corresponding to the DC loop current of the line and the ringing AC signal, for example, pair-type photocouplers 24-1 and 24-2. A varistor 25 for protecting the photocoupler is connected in parallel to the couplers 24-1 and 24-2.

The output side of each photocoupler 24-1 and 24-2 and the input terminal 26 for the dial mask signal DM take the logical product of them.
Logic circuit of, for example, two-input first and second AND gates 27-
A second logic circuit, such as a 2-input OR gate (hereinafter referred to as an OR gate) 28, which is connected to 1, 27-2, and takes the logical OR of the AND gates 27-1 and 27-2 It is connected. The dial mask signal DM supplied to the input terminal 26 is the AND gate 27- during dialing of the own telephone.
It has a function to close the output of the regular AC reception signal and the confusing pseudo AC signal by closing 1,27-2. AND
The signals LA and LB output from the gates 27-1 and 27-2 become the signal S28 at the OR gate 28.

To the output side of the OR gate 28, for example, a one-shot circuit (monostable multivibrator) 29 having a time constant of 100 ms or more and triggered by the signal S28 is connected, and an AC reception signal output from the one-shot circuit 29. Sa is sent to the output terminal 30. The output side of each AND gate 27-1, 27-2 has a signal LA, L for detecting a DC loop and an AC received signal.
Output terminals 31-1 and 31-2 that output B are connected.

FIG. 3 is a signal waveform diagram of FIG. 1, and the operation of FIG. 1 will be described with reference to FIG.

It is assumed that the contact 22 is connected to the telephone terminal 21 side.
First, in a standby state in which the telephone handset is not raised and the ringing AC signal Si is not applied to the telephone line terminal 20, the dial mask signal DM of the input terminal 26 is at the H level and the telephone line terminal 20 Since the photocouplers 24-1 and 24-2 inserted in series between the telephone terminals 21 are off and off, the output signals LA and LB of the AND gates 27-1 and 27-2 become H level. There is. Here, when the calling AC signal Si as shown in FIG. 3 is applied to the telephone line terminal 20, a current flows through the telephone terminal 21 due to the positive and negative voltages of the calling AC signal Si.
The pair-type photocouplers 24-1 and 24-2 repeat the off and on states and the on and off states.
Pulsed signals LA and LB as shown in the figure are output. The signals LA and LB are ORed by the OR gate 28, and the signals of FIG.
It is given to the one-shot circuit 29 in the form of S28. Then,
The one-shot circuit 29 is triggered and outputs a signal Sa as shown in FIG. At this time, the ringing AC signal Si is 16 Hz when the telephone line, that is, the cycle is 62.5 ms, and the time constant of the one-shot circuit 29 is set to 62.5 ms or more,
When a normal ringing AC signal Si is applied to the telephone line terminal 20, the output signal Sa of the one-shot circuit 29 is continuous as shown in FIG. Therefore, by detecting the presence of an incoming call by counting the continuous time of the signal Sa with a microprocessor (not shown) and stopping the calling operation based on that, it is possible to prevent the collision of the incoming and outgoing calls. . Since the output signal Sa of the one-shot circuit 29 is not continuous with respect to line noise, erroneous detection due to noise can be prevented.

Then, when the handset of the telephone is lifted, a direct current loop is formed by the telephone, and the paired photo coupler 24-1,
DC current flows through 24-2, and the photocouplers 24-1 and 24-2 are turned on / off or turned off / on. The photocouplers 24-1 and 24-2 are in one of the above states depending on the direction of the current. As a result, AND gates 27-1 and 27-2
Output signal LA or LB of H becomes high level. Here, when the telephone number of the other party is dialed by the telephone and the other party answers, the polarity of the telephone line is reversed, so the ON / OFF states of the paired photocouplers 24-1 and 24-2 are reversed, and AND The state of the output signal LA or LB of the gate 27-1 or 27-2 is reversed. Therefore, the signal L
By monitoring A and LB, it is possible to detect the polarity reversal, that is, the reverse due to the partner's response.

The present invention is not limited to the embodiment shown in the drawings, and for example, a reed relay other than the pair-type photocouplers 24-1 and 24-2, a switching element or the like may be used as the detection circuit,
Alternatively, various modifications can be made, such as configuring the logic circuit with a circuit other than the OR gate 28, or adding another element to the first circuit.

(Effect of the Invention) As described in detail above, according to the present invention, the ringing AC signal is detected by the detection circuit, and the detected signal is detected by the first and second signals.
Since it is given to the one-shot circuit through the above logic circuit and the one-shot circuit is operated, the continuity of the ringing AC signal can be accurately and easily confirmed based on the output of the one-shot circuit. Preventive effect can be expected. Moreover, based on the dial mask signal, it is possible to easily prevent the pseudo AC signal from being output at the time of dialing by the first logic circuit, so that it is possible to accurately prevent inconvenience such as malfunction. Moreover, reverse can be detected accurately and easily from the signal output to the output terminal through the detection circuit and the first logic circuit based on the ringing AC signal. Therefore, it can be used for various communication terminal devices such as a facsimile and a data terminal, which are connected to a line together with a telephone to detect an incoming call automatically.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a network control circuit showing an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional network control circuit, and FIG. 3 is a signal waveform diagram of FIG. 20 …… telephone line terminal, 21 …… telephone terminal, 22 …… contact,
23 …… Device, 24-1, 24-2 …… Pair type photo coupler, 27-
1, 27-2 ... AND gate, 28 ... OR gate, 29 ... one-shot circuit, 30, 31-1, 31-2 ... output terminal, Si ... call AC signal.

Claims (1)

[Scope of utility model registration request] 1. A network control circuit connected between a line and a communication terminal device for switching connection of the line to the communication terminal device, wherein the network control circuit responds to a DC loop current of the line and a ringing AC signal.
A detection circuit which outputs two logic signals; a first logic circuit which inputs the two logic signals and gate-controls the outputs of the two logic signals based on a dial mask signal; and an output from the first logic circuit Two logical signals
An output terminal for outputting to a mechanism capable of detecting line reverse, a second logic circuit for taking a logical sum of two logic signals output from the first logic circuit, and a time longer than the cycle of the ringing AC signal. A one-shot having a constant number and triggered by the output of the second logic circuit.