For maintenance or even development if working with analog signalling systems e.g radio communicationsMore than 10 available Part of the FX107/207/307 family of signalling devices from CMLThese chips are new old stockBased on a 3 tone sequential signalling system, this device will decode 8 different input codes and provides output in binary form.These were commonly used in radio communication links for the purposes of link control.I have other CML devices in the same family advertised separatelyCML MicroFX3073 Tone Signalling DecoderCeramic DIP package 16 pinDatasheets are availableThese are now extremely hard to find and if you can find them, very long lead time