JPH0754954B2 - Line monitoring method for modem with network controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A signal monitor circuit is provided in a network control device for switching and connecting a modem or a telephone to a telephone line. The signal monitor circuit applies a DC voltage to the telephone during data communication, and the telephone is hooked off. As a result, the direct current is supplied and a part of the received signal of the modem is superimposed on the direct current through the series circuit of the operational amplifier and the capacitor, so that the received signal can be monitored by the telephone.

[Industrial application field]

The present invention relates to a line monitor system for a modem with a network controller.

[Conventional technology]

A network control unit (hereinafter referred to as NCU) is a device used when connecting a terminal device or the like to a public switched line network, and is a device for controlling a public switched line for sending dial pulse or calling record, detecting ringing tone, and the like. However, in recent years, it has been often designed and manufactured in the form of being integrated with the modem in terms of structure and circuit.

FIG. 3 is a diagram showing an example of a conventional NCU.

In the figure, 1 is a terminal, 2 is a modem, 3 is an NCU, 4 is a telephone,
5 is a telephone, 10 is a changeover switch, 11 is a hook switch,
12 is a ringing signal detection circuit (RI), 13 is a polarity reversal detection circuit (RV), or a hook-off detection circuit, 14 is a hybrid,
Reference numeral 15 is a touch-tone signal (DTMF) generation circuit (PB), 16 is a volume, and 17 is a speaker. The same symbols represent the same objects throughout the drawings.

The conventional device configuration on the data terminal side is terminal 1, modem 2, NC
It consists of U3 and telephone 4, and when the changeover switch 10 in the NCU 3 is pushed down to the telephone 4 side, the telephone line 5 is connected to the telephone 4 and it is possible to talk, and when the changeover switch 10 is pushed down to the modem 2 side, the telephone line 5 Can be connected to the modem 2 for data communication.

The call signal detection circuit 12 (hereinafter RI12) is a circuit for detecting a call signal sent from the telephone line 5, and the polarity reversal detection circuit 13 (hereinafter RV13) detects the polarity reversal of the telephone line 5. Then, the end of communication is determined. A touch-tone signal (DTMF) generation circuit 15 (hereinafter referred to as PB15) is a touch-tone signal generation circuit.

In the conventional AA type NCU4 capable of automatic transmission, a speaker 17 is built in as shown in Fig. 3 in order to hear dial tone and busy tone during automatic transmission, and data communication is performed by connecting with the other party from the time of hook-off. Until just before the state, the speaker 17 was sounded and monitored. Of course, in this case, it is desirable that the speaker 17 has its volume 16 variable according to the environmental conditions and the reception volume.

[Problems to be solved by the invention]

However, as described above, it is structurally difficult to bring the volume 16 out of the processor chip in a device incorporating a microprocessor in which the circuit configuration of the NCU 4 and the modem 2 is integrated. I couldn't make any adjustments. As a method of adjusting the volume 16, it is possible to send a command to the processor by operating the keyboard etc., but it takes time to operate the keyboard, and it may take a long time, a sound that is too loud or a sound that is too quiet. There was a problem that it would come out.

[Means for Solving the Problems] As shown in the principle diagram of FIG. 1, the above problems involve switching and connecting one of the modem 2 and the telephone 4 to the telephone line by the first relay contacts 10a and 10b. In the network control device 3, when the telephone line 5 is connected to the modem 2 side, a direct current supply circuit 41 for supplying a direct current to the telephone 4 by hook-off of the telephone 4 and an input line of the modem 2 And a direct current supply circuit 41, and a signal monitor circuit 40 including an operational amplifier 21 and a series circuit 42 of a capacitor 22 for branching a received signal from the telephone line 5 to the modem 2 to the direct current supply circuit 41. Is provided, and the DC supply circuit 41 and the series circuit
The connection point of 42 is connected to the telephone 4 through the second relay contacts 10c and 10d which are closed while the telephone line 5 of the applicant is connected to the modem 2 side, and the electric telephone line 5 is connected to the modem 2 When the telephone 4 is connected to the side and the telephone 4 is hooked off, the received signal amplified by the operational amplifier 21 which is branched from the series circuit 42 is superimposed on the DC current supplied from the DC supply circuit 41. It is solved by supplying to the telephone 4.

[Action]

In accordance with the present invention, the signal monitor circuit 40 includes a telephone line 5 and a modem 2
, The DC voltage V is applied to the telephone 4 and the telephone 4 is hooked off to supply a DC current, and a part of the signal received by the modem 2 is an operational amplifier.
It is superposed on the DC current through a series circuit of a capacitor 21 and a capacitor 22. Therefore, the telephone 4 can monitor the received signal.

〔Example〕

FIG. 2 is a diagram showing an embodiment of the line monitor system according to the present invention.

In the figure, 4a is a hook switch of the telephone 4, 4b is an internal resistance of the telephone 4, 10a and 10b are contacts of the first relay, 10c and 10d are contacts of the second relay, 20 is a DC holding circuit and a primary / secondary separation transformer. (HC), 21 is operational amplifier, 22 is capacitor, 23, 24
Are transistors, 25 to 29 are resistors, 30 is an NCU according to the present invention, and 40 is a signal monitor circuit.

The present invention uses the telephone 4 for the line monitor instead of the conventional volume 16 and speaker 17.

When making a call, the first relay and the second relay are turned off.
At this time, the contacts 10a, 10b of the first relay, the contacts of the second relay
10c and 10d have the contact positions shown, and the telephone line 5 is the telephone 4
And the HC 20 on the modem 2 side is disconnected from the telephone line 5.

When performing data communication, the first relay and the second relay are turned on. At this time, the contact points 10a, 10b of the first relay and the contact points 10c, 10d of the second relay are in the contact positions opposite to those shown in the drawing, the telephone line 5 is connected to the HC 20 on the modem 2 side, and the telephone 4 is connected to the telephone line
Get out of.

The signal monitor circuit 40 according to the present invention comprises transistors 23, 24.
And a DC circuit 42 including an operational amplifier 21 and a capacitor 22.

Since the telephone 4 is used for monitoring when performing data communication, a DC voltage + V is applied to the telephone 4 by the DC supply circuit 41 including the transistors 23 and 24. When the hook switch 4a of the telephone 4 is closed in this state, a direct current flows through the contacts 10c and 10d of the second relay, and the telephone 4 can be used as a monitor.

In the DC supply circuit 41 including the transistors 23 and 24, when the hook switch 4a of the telephone 4 is closed, the collector current of the transistor 23 flows through the internal resistance 4b of the telephone 4 due to the power supply voltage + V.

Therefore, a voltage drop occurs between the terminals of the resistor 26, the transistor 24 is turned on, and an output voltage is produced between the terminals of the resistor 25,
This output voltage can be used as a hook-off signal for the telephone 4.

On the other hand, the signals to be monitored are the output of the HC 20, the series circuit 42 of the operational amplifier 21 and the capacitor 22, and the contact 10 of the second relay.
Since it is sent to the telephone 4 via c and 10d, the received signal can be monitored by the telephone 4.

(1) When manually making or receiving a call using the NCU 30 according to the present invention, the telephone 4 with the first relay and the second relay turned off
After hooking off and dialing, the first relay and the second relay are turned on, and then data communication is started.

(2) When making an automatic call using the NCU 30 according to the present invention, the first relay and the second relay are turned on, and the dial tone of the HC 20 output is confirmed by the telephone 4 via the operational amplifier 21 and the capacitor 22.

In the case of a touch-tone signal, a push-tone signal is generated from PB15 through HC20.

In the case of a dial signal, the first relay is turned on / off to generate a dial pulse.

When the other party is connected, activate the modem 2 and check the connection.
Performed by RV13.

(3) When making an automatic incoming call using the NCU 30 according to the present invention, the ringing signal is detected by the RI 12.

(4) When cutting using the NCU 30 according to the present invention,
Turn off the first relay and the second relay.

(5) When monitoring is performed using the NCU 30 according to the present invention, the first relay and the second relay are turned on, the telephone 4 is hooked off, and monitoring is performed via the operational amplifier 21 and the capacitor 22.

〔The invention's effect〕

As described in detail above, according to the present invention, since it is possible to monitor using a telephone that has been conventionally used, it is possible to monitor without providing a monitor speaker or the like in the network control device. At the same time, hook up the phone only when you need a monitor and listen to the received signal tone.
Since the monitor sound is not output unless the hook is turned off, there is no need to consider the monitor on / off switch or monitor volume adjustment volume, etc., as in the case of constant monitoring with speakers, which is economical. In addition, there is a great effect that a monitor function that is extremely easy to use can be provided.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention. FIG. 2 is a diagram showing an embodiment of the line monitor system according to the present invention. FIG. 3 is a diagram showing an example of a conventional NCU. In the figure, 1 is a terminal, 2 is a modem, 3 is an NCU, 4 is a telephone,
5 is a telephone, 10 is a changeover switch, 11 is a hook switch,
12 is a ringing signal detection circuit (RI), 13 is a polarity reversal detection circuit (RV), or a hook-off detection circuit, 14 is a hybrid,
15 is a touch-tone signal (DTMF) generating circuit (PB), 16 is a volume, 17 is a speaker, 4a is a hook switch of the telephone 4, 4b is an internal resistance of the telephone 4, 10a and 10b are contacts of the first relay, 10c and 10d. Is a contact of the second relay, 20 is a DC holding circuit and primary / secondary separation transformer (HC), 21 is an operational amplifier, 22 is a capacitor, 23 and 24 are transistors respectively, 25 to 29 are resistors respectively, and 30 is according to the present invention. NCU, 40 is a signal monitor circuit.

Claims (1)

[Claims] 1. A telephone line (5) for one of a modem (2) and a telephone (4) with a first relay contact (10a, 10b).
In the network control device (30) that is switched and connected to, when the telephone line (5) is connected to the modem (2) side, a direct current is applied to the telephone (4) by hooking off the telephone (4). It is connected between the direct current supply circuit (41) for supplying, the input line of the modem (2) and the direct current supply circuit (41), and receives a reception signal from the telephone line (5) to the modem (2). A signal monitor circuit (40) provided with an operational amplifier (21) and a series circuit (42) of a capacitor (22) branched to the direct current supply circuit (41) is provided, and the direct current supply circuit (41) and the direct current circuit are connected. The connection point of the example circuit (42) is connected to the telephone (4) via a second relay contact (10c, 10d) which is closed while the telephone line (5) is connected to the modem (2) side. The telephone line (5) is connected to the modem (2) side and the telephone (4) is connected. When turned off, the received signal amplified by the operational amplifier (21) branched by the series circuit (42) is superimposed on the DC current supplied from the DC supply circuit (41), and the telephone (4) A line monitoring system for a modem with a network control device, characterized in that it is configured to be supplied to.