This circuit uses an optical coupler to indicate a phone call through a lamp. The circuit is from a Hands-On Electronics from the 90s. The lamp must be incandescent.
The main feature of this RF oscillator that operates in the range of 100 to 800 kHz is its low...
Many people currently use the bicycle as a means of transportation and leisure in large cities....
In this radio the coil can be made with 70 + 30 turns of wire 28 to 32 in a cardboard or PVC tube...