STANDBY POWER SUPPLY CIRCUIT FOR 2 WIRE BUS INTERCOM SYSTEM AND APPARATUS THEREOF

摘要

A standby power supply circuit (300) for a 2 wire bus intercom system and an apparatus thereof. The standby power supply circuit (300) is separated into two power supply modules in which the first power supply module is a power supply to a standby circuit (302) and the second power supply module is a power supply to an operation circuit (304). The power supply to the operation circuit (304) is switched off by a constant circuit switch (310) when a device load is at the standby status. The power supply to the standby circuit (302) comprises a constant current circuit (306) whose alternating current impedance is large. With the standby power supply circuit the larger alternating current impedance for the 2 wire intercom system is achieved which can offer sufficient power for many device loads both in the conditions of operation and standby status.