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 interesting circuit of 18 multiplexed LEDs was found in the February 1992 issue of Radio...
This circuit is from a 1995 technical documentation. The transistor can be a BC558 and the sensor...
The SCA is a signal superimposed on the FM signals that make it possible to eliminate...