> TI's TCM1520A Ring Detector

No sign of that one locally at retail/catalogue level. Avnet
may have it but they aren't going to sell me just one, so
it's probably a non-starter, but thanks for the suggestion.
I did find this

http://e-www.motorola.com/brdata/PDFDB/docs/MC14LC5447.pdf

which may be a solution, even though initially I wanted to use
bits from the spart parts drawers (may still try a neon JFTHOI).
It would be around NZ$15 (US$7) including tax and p&p. The
job has been put off until after a Thursday meeting, and for the
time being they're happy with an outline on paper. That suits
me as one particular tech issue (out of my hands) has yet to
be resolved, so no point spending up until the project's a goer

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