This circuit is from an 80's documentation, firing when the input voltage exceeds 5 V. The SCR can be the TIC106 need not have a heatsink.
This alarm circuit was found in the July 1992 Radio Electronics magazine. The circuit uses a small...
Found in a Philips publication from the 1970s, this circuit uses a DO040, which is difficult to obtain...
This simple nicad battery charger uses a current regulator with the LM350. This integrated circuit must be...