Single Transistor Nicad Battery Charger

This is a nicad battery charger circuit. Feature : Simple circuitry, charge nicad battery, changeable rate, single transistor, charging current 15mA or 45mA,for 1.5V and 9V battery, 12VAC supply voltage. Component : 1N4001 diode, Capacitor, 1N4148 diode, BD140 transistor, switch, resistor,transforme, Fuse.[zen22142.zen.co.uk]

Balanced microphone preamp

The following circuit is a balanced microphone preamp. Feature : Simple circuitry, inexpensive, 60dB amplification, 12V supply voltage. Component : Resistor, transformer, potentiometer, ne5532, rectifier, 7812, 7912, fuse, capacitor, 7805, zener diode. [nomad.ee]