The circuit shown consists of a power stage for relay excitation. 2N3053 can be a BD135 and 2N406 can be replaced with a BD136. R3 depends on the trigger voltage.
This circuit is suggested by Motorola in its 1990 Linear Databook. The speaker (or headphone is 32...
This circuit was found in a William Sheets. It has 75 ohms of output impedance and can operate up to 20...
This follower, found in a 1982 documentation, has only one amplification step, but it helps in the...