In order to gather biodata in the home environment, we have developed a compact and inexpensive FM multichannel subcarrier system employing micropower integrated circuits of the unique lateral PNP design. The subcarrier system may be used with or without a wireless transmitter. One FM transmitter design that has been used is presented. Components for four channels are mounted on a glass epoxy circuit board. More channels may be added and the potential for hybrid film packaging was considered in the design. Standard IRIG 7.5% proportional subcarrier frequencies from 400 Hz (ch. 1) to 3000 Hz (ch. 8) may be used with the center frequency being determined by the value of a single component in the oscillator circuit. The overall simplicity, stability, fidelity, and low power requirements of this subcarrier system facilitate long term unattended recording.
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