This circuit by Ferranti, in a 1967 publication, is intended for reading perforated tapes. The circuit uses transistors from the era that can be replaced by modern equivalents.
This circuit generates frequencies determined by R3 and C1. We found it in the Radio Electronics magazine...
The configuration below is suggested by the National Semiconductor Linear Applications Handbook. The...
This charger circuit provides an initial voltage of 2.5 V and when the current reaches 180 mA the...