P4802ACMC datasheet(102/212 Pages) TECCOR

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SIDACtor® Data Book and Design Guide

T1/E1 Circuit Protection

T1/E1 networks offer data rates up to 1.544 Mbps (2.058 for E1) on four-wire systems.

Signal levels on the transmit (TX) pair are typically between 2.4 V and 3.6 V while the

receive (RX) pair could go as high as 12 V. Loop powering is typically ±130 V at 60 mA,

although some systems can go as high as 150 V. (Figure 3.16)

Figure 3.16 T1/E1 Overview

Protection Circuitry

Longitudinal protection is required at the Central Office Terminal (COT) interface because of

the ground connection used with loop powering. (Figure 3.17) Two P1800SC MC SIDACtor

devices provide overvoltage protection and two F1250T TeleLink fuses (one on Tip, one on

Ring) provide overcurrent protection. The P1800SC MC device is chosen because its VDRM

is compliant with TIA-968 regulations, Section 4.4.5.2, “Connections with protection paths

to ground.” These regulations state:

Approved terminal equipment and protective circuitry having an

intentional dc conducting path to earth ground for protection purposes at

the leakage current test voltage that was removed during the leakage

current test of section 4.3 shall, upon its replacement, have a 50 Hz or

60 Hz voltage source applied between the following points:

a. Simplexed telephone connections, including Tip and Ring, Tip-1

and Ring-1, E&M leads and auxiliary leads

b. Earth grounding connections

The voltage shall be gradually increased from zero to 120 V rms for

approved terminal equipment, or 300 V rms for protective circuitry, then

maintained for one minute. The current between (a) and (b) shall not

Central Office

Line powered DLC Four-wire,1.544 Mbps/2.048 Mbps

T1 Transceiver

TX Pair

3000 ft

6000 ft

RX Pair

Line Regenerator

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