This interesting circuit found in American documentation generates a busy signal, without you having to take the phone off the hook if you do not want to answer. The components used are common.
circuit is used to increase the sensivity of a relay. A 50 to 100 mA relay can be triggered with...
The configuration shown makes use of a simple source and the gain is given by the relationship between R3...
This blinker consists of a simple multivibrator and instead of the lamp, an LED and a 470 ohms...