A transmitter surely requires receiver. Receiver meant here is a functioning device as transmitter couple at transmitter infrared is upper. Obtainable moderation by force of a FET.
Light infrared is falling at photodiode infrared (BPW 34 or can apply other type) make strain will at R1 varies. This thing will influence spandrel VFET and bleeder current, so that result of its will fluctuate according to modulation of light infra red received. this audible modulation by using headphone.
This moderation of course has loss. For example tube lamplight animated at area of around this device will be heard as whizzing noise. At quiet condition, good enough acceptance receiving possibly can be done at distance some meter. This thing is extendable with help of lens or equipments of other optic. With a few fruit of infrared LED and a diode photo, this transmitter combination trap and receiver can be made easily. This circuit can work carefully and suited for experiments.
One thing again, if we like to worked carefully, P1 must be stele in such a manner, so that at the time of diode is hindered to light, measurable strain at bleeder FET precise would equal to semi strain power supply
