For maintenance or even development if working with analog audio tone control systems, particularly radio linksPart of the FX family of signalling devices from CMLCML MicroFX205Tone EncoderThese chips are “pulls” from a decommissioned communications systemGenerating tones from 30Hz to 5Khz with a pseudo sine waveform output, the frequency of which is set externally by an RC network.Gated, time burst and amplitude variation are all controllable externally.Typically it uses a supply of 12V (range is 11 – 15V) @7mASealed metal can, 8 legs – all are gold plated
I have other CML devices in the same family advertised separatelyDatasheets/application notes are availableThese are now extremely hard to find and no longer in production