JPS5870675A - Surge protecting system - Google Patents

Abstract

PURPOSE:To economically perform the protection against surge current and voltage incoming to a subscriber circuit unit, by connecting the units with a DC balanced transmission circuit and a common mode choke. CONSTITUTION:A surge incoming to a subscriber line is absorbed with a surge absorbing circuit in the 1st unit and that mounted in an MDF installed in an exchange station to avoid the surge from being applied to each circuit of the 1st unit. In order to prevent the surge from being applied to various circuits in the 2nd and succeeding units and devices via a pair of signal lines 15 being an interface with the 2nd unit, when the surge appears at the output of an amplifier 16, the surge energy is absorbed with a choke coil 17 to improve the surge- resistance between both the units.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for protecting against lightning surges and the like in a concentrator of a digital exchange.

In conventional line concentrators using mechanical contacts, subscriber lines and various control devices were electrically insulated, so they were not affected by lightning surges induced in subscriber lines. However, the above-mentioned electrical insulation cannot be ensured in the concentrator devices of digital exchanges that have appeared due to the recent advances in LSI technology. Therefore, it has become essential for the line concentrator to introduce some kind of surge protection method.

As a perfect means, it is conceivable to connect the subscriber line and the subscriber circuit provided individually for each subscriber to the concentrator using an optical coupling element, but each has its own advantages in terms of response speed, reliability, and economic efficiency of the wrinkle element. However, it is an object of the present invention to provide a system that reasonably achieves the intended purpose of surge protection by providing a power supply/earth system in the unit waste.

In order to achieve the above object, the present invention takes economic efficiency into consideration and uses the line concentrator 21! N subscriber circuits are divided into purchasing units and installed individually for each subscriber, and one circuit is installed for each of the N circuits.
A first unit is made up of two interface circuits, and a second unit is connected to the location of the first unit and performs line concentration and multiplexing for (NXm=)M subscribers. In order to prevent damage caused by surge intrusion from reaching the @2 unit, the power supply/ground system is connected to the first unit. The second unit is provided separately, and both units are connected by a DC balanced transmission circuit and a common mode choke.

Embodiments of the present invention will be described in detail below with reference to nine drawings.

FIG. 1 shows a line concentrator, ToFt 1a, the first unit, 2 the subscriber circuit for the N subscribers, 3 the interface circuit provided for the circuit, 4°5, 6.7.
8 is various power supply and ground foot used in the first unit;
4 is -43v (first power supply supplied to the terminal via the subscriber line). 9 is a connection from the first power source to the second power source (
+5v for analog).

The first power supply part creates the third power supply (-3V for analog PG) and the fourth power supply (digital +SV), and 5 to 7 are the second power supply part.
˜4th power supply, and 8 is the first ground used by the first unit. 10 is the second unit), 11 is a second unit that creates the fifth power supply (digital +5V) from the 4
12 is a second ground used by the 20th unit.

It is connected to the power supply/earth system of Class 28. 15 shows the signal lines exchanged between the units.

Figure 2 shows an inter-unit connection circuit showing details of the relationship 3.10.15 (signal interface method) in Figure 1. 16 is an unbalanced/balanced conversion circuit, 17 is a common mode choke, 18 is a balanced/unbalanced conversion circuit, and 19.20 is a matching resistor.

Surges entering the subscriber line are absorbed by the surge absorption circuit in the first unit and the surge absorption circuit mounted on the MDF installed in the exchange, so that they are not applied to each circuit in the first unit. Of course, the signal line 15 shown in FIG. 111! Protected by format.

That is, when a surge appears in the output of unit 16, it is absorbed by choke coil 17 and the surge energy is reduced, thereby making it possible to improve the surge resistance between both units. Of course, the value of each inductance must be selected so as not to affect the original signal transmission. Further, as the inductance value increases, the surge resistance between the four units described above improves.

Figure 2 explains the connection format for the signal line when sending from the first unit and receiving from the second unit, but the signal line when sending from the second unit and receiving from the first unit This can also be handled in the same way as in FIG.

According to the invention, it is economically possible to protect against surge currents and voltages entering the subscriber circuit unit, and also against surge currents and voltages generated in the mosquito subscriber circuit entering the concentrator multiplexing unit. becomes.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the power supply/earth system in the line concentrator, and Figure 2 is a diagram illustrating the signal # connection format between units. l ・・・・・・・・・・First unit 2・・・・
......Subscriber circuit 3 for N subscribers...
・・・・・・・・・(7 terminals 7 terminals circuits 4 to 8...
・・・・・・Various power supplies and grounding 9 ・・・・・・・・・
・・10th power supply section 10 ・・・・・・・・・・・・
Unit 11 of ljg2 that executes concentrating multiplexing...
...... Second power supply section 12 ......
...Second Earth 13 ......
...Second unit main body part 16 ......
...Unbalanced balance conversion circuit 17 ......
・・Common mode choke 1B ・・・・・・・・・・・・
・・Balanced unbalanced conversion circuit Z 9120 ・・・・・
Matching resistor Continued from page 1 ■Applicant: NEC Corporation, 5-33-1 Shiba, Minato-ku, Tokyo ■Applicant: Hitachi, Ltd., No. 1 Marunouchi-chome, Chiyoda-ku, Tokyo

Claims (1)

[Claims] In a surge protection method for protecting against intrusion of surge voltage and surge current induced in a subscriber line. N subscriber circuits installed to correspond to subscriber lines (N < N: an integer of 2 or more) and one interface circuit installed for the N subscriber circuits. ) A subscriber circuit unit group is composed of m (m: an integer of 2 or more), and a line concentrator/concentrator that interfaces with the m units.
A multiplexing unit is provided. The subscriber circuit unit is composed of the same first power supply/earth system, and the concentrator/multiplex chemical unit is composed of a 20th power supply/earth system which is different from the power supply/earth system, and DC balance is established between both units. A surge protection method characterized by a connection between a transmission circuit and a common mode choke.