This circuit turns on an old cassette recorder when the telephone rings, thus enabling the telephone conversation to be recorded. Transistors are general purpose types. The circuit is from an 80's documentation.
This photo-relay uses a Darlington stage to increase sensivity. Any photo-transistor can be used....
This circuit monitors the current of a series of 40 V lithium battery packs connected in series....
Launched in early 1999, the new ADC12181 high-speed A / D converter is suitable for applications...