Importance

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Abstract

A detector circuit for detecting the loss or reduction of dc power to a dc load and for detecting a low battery voltage condition of a standby battery employed to power the load upon loss or reduction of dc power supplied to the load. The dc voltages for use by the dc load and for charging the battery are derived from a dc power supply circuit with which the detector circuit of the present invention is used. The detector circuit of the invention includes a first voltage monitoring circuit operative to examine a dc voltage at a predetermined point in the dc power supply circuit and when the value of this dc voltage is less than a predetermined value indicating a loss of power to the dc load to cause a transfer circuit to couple the battery and the dc voltage thereacross to the dc load. Following this coupling operation, the transfer circuit receives the dc voltage coupled from the battery to the load and maintains the battery coupled to the load. The detector circuit further includes a second voltage monitoring circuit operative following the abovementioned coupling operation to examine the value of dc voltage coupled to the dc load from the battery and when the value of the dc voltage is less than a predetermined value to cause the transfer circuit to uncouple the standby battery and the dc voltage thereacross from the dc load.

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First Claim