We found this circuit in an old documentation, but it is still current. General purpose transistors can be used, and the SCR can be the TIC106. The bell is a transducer with an oscillator (buzzer).
This circuit is from the manual of the integrated circuit used. Similar versions appear on this...
We found this circuit in the 1993 Motorola Linear Interface ICs. The operational is unusual today, but...
We found this circuit in a publication with experiments with operational amplifiers from 1973. The...