We found this circuit in the 1957 Raytheon transistor application manual. The transistor can be a BC558 and the common 6 V relay, just by using this voltage in the supply.
This circuit was published in an English magazine from 1977, but it can be easily assembled since...
The maximum current of this circuit is 1 A. The circuit is from Motorola Linear Interface ICs from...
This circuit is a handset receiver that picks up the signal emitted by a coil under the rug or...