This well-known circuit version of the siren was obtained in a Colectro Handbook from the 70s. The transistors are of general use, with Q2 being a BD136 for greater power with power from 6 to 12 V.
Found in American documentation from the 90s, this configuration detects the direction of rotation...
This amplifier with a 9 MHz passband and 10 voltage gain with two transistors was found in...
A Schmitt trigger inverter can be obtained from each gate of the 4093 with the connection shown in the...