Suggested by a Popular Electronics from the 90s, this circuit triggers an external load, relay or recorder, when the telephone line receives a call, thus enabling its recording.
This circuit from a 1980 publication, converts the temperature sensed by Q1 into a frequency in a...
This oscillator has its frequency controlled by crystal and its frequency can be between 100 kHz...
The author has many books he had written in Eglish (See the Biography) published by famous...