JPS58168396A - Automatic switching system of insertion loss - Google Patents

Abstract

PURPOSE:To switch a call loss automatically in accordance with subscriber's line length by supervising call current to a telephone set through each subscriber's line. CONSTITUTION:DC current is supplied to a telephone set through resistors R1, R1' and a hybrid transformer TRNS, and when a subscriber hooks off his telephone set, the DC loop is closed and current I is made flow. Since the current I is changed by the line length up to the telephone set, the current I is divided by high resistance R2, R3 and inputted to a comparator CMP. The comparator CMP compares the input value with reference voltage VREF, and when the input voltage is higher or lower than the VREF, the ''H'' level or ''L'' level is outputted respectively, so that electronic switches SW0, SW0', SW1, SW1' are turned on/off to switch the insertion loss.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) The technical aspects of the invention @岨 relate to insertion loss in the subscriber circuit of a telephone exchange.

(Yang) Technical Background Telephone exchanges are used to connect subscriber telephones located within a certain area.
Each subscriber's telephone is connected by a telephone line, but each subscriber's telephone is connected by a telephone line, but the length of each subscriber's telephone is naturally different depending on the installation location, especially in depopulated areas. There are a wide range of subscriber telephones available, and the path lengths of subscribers vary greatly. As a result, the communication current from the exchange to the subscriber's telephone varies greatly depending on the magnitude of the line resistance. In order to guarantee constant call quality, it is necessary to keep the call current constant regardless of the line length, so all lines are set to be approximately equal, especially for telephone calls that require long distance subscriber lines.

('!4 Conventional technology and problems In conventional exchanges, the insertion loss is often not changed depending on the length of the line and the call level differs between subscribers with short lines and subscribers with long lines, which makes it feel strange.) When insertion loss is changed depending on the length of the line, there is a software-controlled switching method as a conventional insertion loss switching method. There is a drawback that the subscriber data must be registered in the software in advance as subscriber data, making it difficult to add more subscribers and to accommodate and change lines.

OBJECT OF THE INVENTION In view of the above-mentioned conventional drawbacks, the present invention monitors the communication current to the telephone in each subscriber's circuit, and if the current flows for more than a certain amount, it is considered that the connection is short and the connection is terminated. The purpose of this invention is to provide an automatic insertion loss switching system that can average the call loss when the subscriber's line is long and short by inserting L08B in the subscriber's circuit.

(5) Structure and object of the invention According to the present invention, the present invention provides a telephone exchange in which the communication current to a subscriber telephone changes depending on the line length between the telephone exchange and the subscriber telephone connected thereto. a circuit for monitoring a communication current that changes depending on the length of the line;
．． An automatic insertion loss switching system is provided, which is characterized by having an amplifier whose gain can be switched by controlling the output of the monitoring circuit.

The drawing is a block diagram of a nine-subscriber circuit to which the automatic insertion loss switching method according to the present invention is applied.

In the same figure, R1~R, and R1/, R, /~R
, / is a resistor, and TRN5 is a hybrid transformer.

opx, opgH opnea', BNq balancing, twerk, 0ODItO is kneader/decoder, OM
F is a comparator, O)i capacitor, 870,8WO'.

≦8Wl, IWI' indicate an electronic switch, and svo indicates an electronic switch control device. The phone has R15R1/
DC current is supplied through TRN3 and TRN3, and when the subscriber HOOKs the telephone -107F.

The DC loop is closed and the electric current flows, and the electric current changes depending on the line length of the five circuits and the telephone engine, thereby changing the voltage at one point of the resistor R1/. High resistance't*
The voltage is divided by R1 and input to the comparator OMF. The comparator compares the reference voltage VRelF, and the input voltage is higher than VRIF.
If qh then Hlc<h If Level Low then Low
w Lsvel , thereby electronic switches swo, swo'.

SWl and SWI' are set to 01110FFν.

The comparator is designed with hysteresis.

The insertion loss switching circuit uses an inverting amplifier using an OF amplifier, and gain switching is electronically performed using an analog switch.

The amplifier used in this invention has an analog switch ON.
I am taking the #II type gt where resistance is not a problem.

The electrical requirements for the insertion loss switching circuit are as follows: the direct voltage between point b and point C in the drawing is V., and the resistance value is R1, so that one pair of communication current can be guaranteed for point C and CODRC.

()) Effects of the Invention As explained in detail above, 1. According to the automatic insertion loss switching system of the present invention, insertion loss can be averaged without being aware of the subscriber's path, and construction and maintenance are facilitated. In particular, an extremely large effect can be obtained in reaccommodating subscriber telephones.

[Brief explanation of the drawing]

The drawing is a diagram for explaining an embodiment of a subscriber circuit to which the automatic interpolation loss switching method according to the present invention is applied. In the drawings, R1-R8 and R', R,' to R,'
is the resistor %'fRNB is the hybrid transformer, OP
l. 0P2i operational amplifier, BM is balancing network, 0ODKC is kneader/decoder, OMF is comparator, 0
is a capacitor, 8W0, 8WO, Sfl.

Claims (1)

[Claims] A circuit for monitoring a call type R that changes depending on the line length in a telephone exchange where the call current to a subscriber telephone changes according to the line length of the telephone exchange and the subscriber telephone institution connected thereto. , an automatic insertion loss switching system characterized in that it has a gain switchable intensifier controlled by the output of a wrinkle monitoring circuit.