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Overvoltage_protection_for_telephone_equipment

2016-09-11 12:36  
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Overvoltage_protection_for_telephone_equipment
This circuit shows two SIDACs that are connected to protect the telephone Subscriber Loop Interface Circuit (SLIC) and associated electronics from voltage surges. This is in addition to the primary protection provided by the gas-discharge tube across the tip and ring lines. If a high positive-voltage transient appears on the lines, D1 (with a peak-inverse voltage of 1000 V) blocks the pulse, and the corresponding SIDAC conducts the surge to ground. Conversely, D2 and the related SIDAC protect the SLIC from negative transients. The SIDACs do not conduct when normal signals are present.