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Motorola
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Abstract
Typically, battery powered portable communication equipment requires periodic recharging. In most systems it is desirable to maintain communication during this recharge period. In order to provide continued communication while charging, the charger, thru control lines interconnected with the por- table device, is designed to disable high current sections of the portable device while providing duplicate functions to those of the portable device. This minimizes the current requirements of the por- table and in turn reduces the time required for recharging.
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iM? MOTOROLA
Technical Developments Volume 3 March 1983
EMERGENCY POWER SWITCH
By Don Branner
Typically, battery powered portable communication equipment requires periodic recharging. In most systems it is desirable to maintain communication during this recharge period. In order to provide continued communication while charging, the charger, thru control lines interconnected with the por- table device, is designed to disable high current sections of the portable device while providing duplicate functions to those of the portable device. This minimizes the current requirements of the por- table and in turn reduces the time required for recharging.
4 An additional step in maintaining communication is achieved with the Emergency Power Switch circuit (Fig. 1.) This circuit will immediately restore functional control to the portable device if AC power to the charger is lost.
VRl is selected for a Vz at some point below the charger's B+ line to be monitored. VW's switch- ing point is determined by the monitored B+ line variation, the decay characteristics of the B+ line when AC power is removed and the switching time requirements of the portable device VRI, normally conducting, allows switch Ql thru Qn to turn on. Ql thru Qn provide the disable inputs for the portable device. It should be noted that any number of switch interface circuits can be placed between VRl and the portable device. If the voltage across VRl drops below its control region it will essentially open...
