Using this circuit diagram can be designed a very simple proximity detector using a temperature sensor. The temperature sensor can react to any heat generated by body heat. The sensor used has a sensitive surface which was divided in two, so that it can sense if the heat source is coming from the left or right. Indication for cold objects will be exactly opposite of the warm objects.
IC1b form a symmetrical power circuit. Terminal "s" is the sensor output. Signal over the "s" will be amplified in IC1a, with a gain factor of 70, before being delivered to the output detector.