JPS63136747A - Communication equipment - Google Patents

Abstract

PURPOSE:To realize a MODEM/telephone line interface satisfying the insulation resistance between power supply and a line specified by the technical standards with small size and light weight by using an optical isolation amplifier so as to couple the input/output of a speech network IC and a MODEM. CONSTITUTION:A DC resistance (50-200ohms) and an AC impedance (600ohms) viewed from a telephone line are kept as specified by a resistance hybrid and a speech network IC. Moreover, the input/output of the speech network IC and MODEM uses an optical isolation amplifier 24 (an amplifier comprising an optical coupler and an operational amplifier or a transistor whose input/ output is isolated electrically) and is coupled while keeping electric isolation. A constant current circuit 22 and a stabilizing circuit 23 supply power to elements of an optical isolation amplifier to the telephone line side. The operational amplifier, the transistor, the speech network IC or the like are easily of surface mount type, and no large sized component such as a transformer and a nonpolar large capacitor is not required and the small size/light weight of the circuit is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an interface system between a modem and a public telephone line.

[Conventional example]

Conventionally, this type of apparatus, such as a facsimile machine, has been constructed as shown in FIG. In the figure, 1 is a hook switch relay, 2 is a drive circuit for relay 1, 3 is a magnetic reversal detection circuit for response confirmation, 4 is a calling signal detection circuit, and 5
is a blockage wire, 6 is a DC blocking capacitor, 7 is an isolation transformer, 8 is a hybrid circuit (2-wire to 4-wire conversion circuit)
, 9.10 is an amplification amplifier, 11 is a modem, 12 is a selection signal generation circuit, 13 is a central processing unit, and 14 is a telephone line connection terminal. In this case, in order to keep the AC impedance at 600Ω while making the DC resistance 50 to 300Ω, the blockage coil 5 needs to have an iductance of 1 (H) or more and a current capacity of 120mA DC, and
The DC blocking capacitor in the 2.2 μF must also be non-polar, and it is difficult to make these capacitors small due to their shape, which has traditionally been a major hindrance to miniaturizing this type of circuit. It had become.

Furthermore, if we look at Figure 4, which shows an example of an interface between a telephone and a modem using a speech network IC, we can see that there is a connection between the modem's power supply system and the telephone line that exceeds the value specified by technical standards. Although it is necessary to have insulation resistance, speech network ICs were originally developed for telephone use, and were not intended to interface with externally powered devices such as modems. It was extremely difficult to insert isolation using a transformer as shown in FIG.

If a speech network IC and a modem that receives power from an external source are to be coupled, it is necessary to use acoustic coupling as shown in FIG. 4, for example.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional examples, and to provide a communication device that is small, lightweight, and has an insulation resistance between a line and a power source that complies with the technical standards of the Ministry of Posts and Telecommunications.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. 1
1 is a hook switch relay, 2 is a relay drive circuit, 3 is a polarity reversal detection circuit, 4 is a calling signal detection circuit, 11 is a modem, 12 is a selection signal generation circuit, 13 is a central processing unit, 1
4 is a telephone line connection terminal, 16 is a polarity matching diode bridge, 17 is a 2-wire to 4-wire conversion circuit (resistance hybrid) consisting of a resistor and a capacitor, 18 is a speech network IC, 22 is a constant current circuit, and 23 is a voltage stabilization circuit. circuit,
24 is an optical isolation amplifier.

Figure 1 shows automatic transmission/reception (AA) types N, C, and U.
In this example, the selection signal is of the DTMF dial (button phone) type.

The DC resistance (50-200Ω) and AC impedance (600Ω) seen from the telephone line are maintained as specified by the resistive hybrid and speech network IC. In addition, the input and output of the speech network IC and the modem are coupled while maintaining electrical isolation using an optical isolation amplifier (an optical coupler GOP amplifier or an amplifier whose input and output are electrically isolated). A constant current circuit 22 and a stabilizing circuit 23 supply power to elements on the telephone line side of the optical isolation amplifier.

In the above circuit configuration, optical couplers, OP amplifiers, transistors, speech network ICs, etc. can be easily surface-mounted, and there is no need to use large-sized components such as transformers and non-polar large-capacity capacitors. This allows the circuit to be significantly smaller and lighter.

Although the above embodiments have been described with respect to AA type N, C, U, and DATF dials, FIG. 2 shows an embodiment in which a pulse dial is used as a selection signal. Further, as shown in the figure, by connecting a microphone and a speaker that can be switched to input/output from a modem to the speech network IC, it becomes possible to support manual transmission or manual reception.

As explained above, by coupling the input and output of the speech network IC and the modem with an optical isolation amplifier, modems and telephones that are small, lightweight, and satisfy the insulation resistance between the power supply and line specified by technical standards can be created. A line interface can be realized.

〔effect〕

As described above, according to the present invention, it is possible to provide a communication device that has a simple configuration and can be downsized.

[Brief explanation of the drawing]

Fig. 1 shows the configuration of this embodiment (AA type, DTMF dial), and Fig. 2 shows the configuration of other embodiments (MM type, MA type,
Diagram showing the configuration of the AA type (compatible with pulse dial), Part 3
The figure shows an example of a circuit of a conventional modem telephone interface. Figure 4 is an example of an interface between a conventional telephone using a speech network and an external modem (using an acoustic converter).
FIG. 1 is a relay, 2 is a relay drive circuit, 3 is a polarity reversal detection circuit, 4 is a call signal detection circuit, 5 is a blocking wire, 6 is a non-polar capacitor, 7 is a transformer, 8 is a hybrid, 9.1
0 is an amplifier, 11 is a modem, 12 is a selection signal generation circuit,
13 is a central processing unit, 14 is a telephone line connection terminal, 15 is a foot switch, 16 is a diode bridge, 17 is a resistance hybrid, 18 is a speech network IC, 1
9 is a speaker, 20 is a microphone, 21 is an acoustic coupler, 22 is a constant current circuit, 23 is a voltage stabilization circuit, 24 is an optical isolation amplifier, 25 is an optical coupler, and 26 is a transistor.

Claims (1)

[Claims] In a communication device that communicates via a line, there is a modem that demodulates the signal from the line and modulates the signal sent to the line, and a modem that converts the input/output signal of the modem into an optical signal and then sends a signal according to the line. 1. A communication device comprising means for converting the signal into a signal corresponding to a previous modem and outputting the signal to the modem.