Warning system for low battery state in portable instrument - with low frequency auxiliary carrier interrupted when battery supply is low

摘要

An auxiliary carrier signal generator provides a warning system for the low state of a battery used in a transportable transmitter used with high performance instrumentation. In particular the system is appropriate for use with hospital electro-cardiograph equipment. The low frequency transistor-oscillator of the auxiliary carrier system consists of a transistor (1) with an inductance (2) with a feedback winding and capacitor (3) coupled to the base(6) of the transistor over a Zener diode (4) and resistance (5). The supply battery is coupled over terminals (9, 10) and the output (19, 20) transmitted to the receiver. If the battery voltage falls below a minimum value the Zener diode ensures that the auxiliary carrier ceases and an indicator is lit.