JPH0465963A - Network control circuit - Google Patents

Abstract

PURPOSE:To reduce the size of the network control circuit and to constitute the whole circuit as a solid state semiconductor by using a photocoupler for isolation, arranging a 2-line/4-line converter and A/D and D/A converters on the primary side and arranging A/D and D/A converters and a selector on the secondary side. CONSTITUTION:A signal from a subscriber's telephone line is A/D converted by the A/D converter 12 through the 2-line/4-line converter 11 and sent to a telephone set through the photocoupler 13, the D/A converter 14 and the selector 15, and in parallel with said transmission, a signal from the telephone set is A/D converted by the A/D converter 16 through the selector 15 and sent to the subscriber's telephone line through the photocoupler 17, the D/A converter 18 and the converter 11. Since the network control circuit is constituted of the above parts, the use of electromagnetic parts is unnecessary, so that the compact network control circuit allowed to be constituted as a semiconductor can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a network control circuit used when a data terminal, facsimile machine, etc. with a telephone attached is accommodated in a subscriber telephone line, and in particular, The present invention relates to a network control circuit having a structure in which the entire circuit can be made into a semiconductor or solid-state without using electromagnetic parts as components.

[Prior Art] General data terminals and facsimile machines (hereinafter simply referred to as terminals) are generally equipped with telephones, but either the terminals themselves are accommodated in the subscriber's telephone line or the telephones are not accommodated. Switching is controlled by a network control circuit inserted between the subscriber's telephone line and the subscriber's telephone line.

Here, to briefly explain the network control circuit according to the prior art, FIG. 4 shows an example of its general configuration. As shown in the figure, the selective switching accommodation of the telephone and the terminal modem section to the subscriber telephone line is controlled by the switching state inside the switching device 1 via the relay drive section 3 under the control of the terminal internal control circuit. It is now done by. When a terminal modem section is accommodated in a subscriber's telephone line in order to protect the exchange side (primary side), it is accommodated via a transformer 2 for line isolation. An example of this type of technology is Japanese Patent Application Laid-open No. 191746/1983.

[Problem to be solved by the invention] However, in the network control circuit according to the prior art,
Electromagnetic parts such as relays and transformers are used as components, and not only can they not be made smaller or cheaper, but the entire circuit cannot be constructed as a semiconductor or solid-state. There is.

SUMMARY OF THE INVENTION An object of the present invention is to provide a network control circuit which is small in size and low in cost, and in which the entire circuit can be made into a semiconductor or a solid-state.

[Means for Solving the Problems] The above purpose is to use a photocoupler for isolation, while installing a 2-wire 4-wire converter and an A/D-D on the primary side.
This is achieved by configuring the /A converter to have an A/D-D/A converter and a selector on the secondary side, respectively.

[Function] A selector (configured as a semiconductor analog switch) accommodates the telephone or terminal modem section in the network control circuit, but the terminal internal control circuit switches the selector to accommodate the telephone or terminal modem section. is designed to be selectively accommodated. For example, if we assume that a telephone is selectively accommodated in the selector, in this state the signal from the subscriber's telephone line is converted to A/D by an A/D converter via a 2-wire and 4-wire converter. The signal is then sent to the telephone via a photocoupler, D/A converter, and selector, while at the same time, the signal from the telephone is passed through the selector, A/D converted by the A/D converter, and then sent to the telephone. , a photocoupler, a D/A converter, and a 2-wire/4-wire converter to enable transmission onto the subscriber's telephone line. Selective accommodation of telephones and terminal modems is performed by selectors with a semiconductor structure, and data transfer in the isolation part is performed by photocouplers, so the network control circuit eliminates the need for electromagnetic components.
In other words, it is possible to obtain a network control circuit that is small in size, low in cost, and can be made into a semiconductor.

[Example] The present invention will be explained below with reference to FIGS. 1 to 3.

First, the configuration of the network control circuit according to the present invention will be explained. FIG. 1 shows the overall configuration. As shown in the figure, the subscriber's telephone line ＼ is selectively accommodated via the network control circuit (the one within the dashed line display frame) according to the present invention, with the telephone set and the terminal modem section each being selectively accommodated. This is determined by the terminal's internal control circuit. The internal control circuit of the terminal sets the selector 15 (specifically, configured as a semiconductor analog switch) to a predetermined value based on the operation state of the changeover switch from the operation panel of the terminal, the on/off hook state of the telephone, etc. By controlling the network control circuit, either a telephone set or a terminal modem section is selectively accommodated via the selector 15. The network control circuit is also accommodated in the subscriber's telephone line via the 2-wire/4-wire converter 11, but here we will take the case where, for example, a telephone is selectively accommodated in the network control circuit. The operation of the network control circuit in this case will be explained as follows.

That is, the signal from the subscriber's telephone line is sent to the 2-wire 4-wire converter 11.
is converted into a low level signal via the A/D converter 12
It is designed to be A/D converted.

Thereafter, the serial state signal is transferred to the D/A converter 14 via the optical transmitter/receiver (specifically configured as a photocoupler) 13, but the serial state signal is converted into parallel and then transferred to the D/A converter 14. D/A converter 14
After being A-converted, the signal is sent to the telephone via the selector 15 as an analog signal. on the other hand,
In parallel with the above operations, the signal from the telephone is A/D converted by the A/D converter 16 via the selector 15, and then
The serially converted data is transferred to the D/A converter 18 via an optical transmitter/receiver (specifically configured as a photocoupler) 17. The serial status signal to the D/A converter 18 is sent to the D/A converter 18 after parallel conversion.
2 after being D/A converted and converted to analog.
It is transmitted via a four-wire converter 11 onto the subscriber's telephone line.

FIG. 2 also more specifically shows the internal configuration of the A/D converter 12 and the D/A converter 18, as well as their peripheral circuits. As shown in the figure, the analog signal from the subscriber's telephone line that has passed through the 2-wire 4-wire converter 11 is cut off at a frequency of 172 of the sampling rate by the shaping filter 21, so that its harmonic signal components are is removed, and is then A/D converted by the A/D converter 22 based on the sampling clock from the clock generator 26. During the A/D conversion, a reference voltage is generated in the reference voltage generator 25 from the current supplied from the subscriber's telephone line.
By comparing the level of the analog signal to the converter 12, the A/D conversion operation in the A/D conversion section 22 is controlled. That is, when the analog signal level exceeds the reference level, the A/D conversion bit is set to the maximum value data, and when the analog signal level is below the reference voltage, linear A/D conversion is performed. This is how it is done. The parallel A/D conversion bits from the A/D conversion section 22 are serially converted and then sent to the optical transceiver 13. In the optical transceiver 13, as shown in FIG. 3, the serial A/D conversion bit is used to control the light emission drive of the photodiode 31, and the phototransistor 32 is controlled on/off by the optical signal from the photodiode 31. In this way, the analog signal from the subscriber's telephone line is transferred to the secondary side in the form of a digital signal, with the primary side and the secondary side electrically separated. In the past, weak analog signals could not be transferred to the secondary side, but with data transfer as described above, even weak signals can be reliably transferred to the secondary side, and D/A The signal is converted back to the original analog signal by the converter 14 and then sent to the telephone. In this situation, the signal from the telephone is A/D converted, D/A
The same applies to conversion. In any case,
When being D/A converted, in the case of A/D conversion bit maximum value data, the reference voltage from the reference voltage generation section 25 is obtained as the D/A conversion output.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain a network control circuit which is small in size and low in cost, and in which the entire circuit can be made into a semiconductor or a solid-state.

[Brief explanation of the drawing]

FIG. 1 shows the overall configuration of the network control circuit according to the present invention, and FIG. 2 shows the A/D converter and D
FIG. 3 is a diagram showing the specific configuration of the optical transmitter/receiver, and FIG. 4 is a diagram showing the network control according to the prior art. FIG. 1 is a diagram showing a general configuration of a circuit. 11...2-wire 4-wire converter 12.16...A/D converter 13.17...Optical transceiver 14.18...D/A converter 15...Selector Figure CC2 figure

Claims (1)

[Claims] 1. Used when accommodating a data terminal or facsimile device with a telephone attached to a subscriber's telephone line,
A network control circuit configured such that either a telephone or a terminal modem section is selectively accommodated in a selector under the control of a terminal internal control circuit, and the network control circuit is configured to selectively accommodate either a telephone set or a terminal modem section in a selector under the control of a terminal internal control circuit. 1 A/D converter, a first optical transceiver,
The selector sends a signal from either the telephone or the terminal modem section via the first D/A converter, and the signal from the telephone or the terminal modem section is sent from the selector to the second A/D converter.
A network control circuit configured to transmit data from a 2-wire/4-wire converter onto a subscriber's telephone line via a converter, a second optical transceiver, and a second D/A converter.