ZN414

The ZN414 was popular amongst hobbyists, as a fully working AM radio could be made with just a few external components, a crystal earpiece and a 1.5 V cell.

Later variants, the ZN415 and ZN416, came in 8-pin DIL packages and included a built-in amplifier that could drive headphones and small speakers directly.

The TRF design is much simpler than the popular, but more complex, superheterodyne radio circuit often used in modern AM receivers.

CDI was invented by engineers at Bell Telephone Laboratories and subsequently developed into a commercial process by Ferranti in the UK.

The current consumption is so low that a 1.8 V red LED (not the 2.2 V high efficiency types) can be used as a shunt regulator from 3 V batteries or a 5 V supply.