This circuit generates the busy tone of ordinary telephones. The transistors can be the BC548 and the components of the T filter and the multivibrator can be changed to obtain the exact tone.
This circuit uses a simple power source, having been found in the Philips Databook of 1990....
This circuit is suggested by Texas Instruments in its Linear Circuits Applications. It is a...
This circuit generates a pulsed tone whose frequency depends on C2 and whose flashing depends on...