Can anybody suggest any efficient audio fed-back mechanism through telephone line so that the telephoning person can hear audio beeps, by which he can check the status of remotely controlled device (teleremote control). I have tried two circuits (see two attached files)
But cannot hear any sounds at remote calling end. I have tried all frequencies in the range 300-650Hz by varying POT in the 555 astable audio beeps generator. But no result.
I have selected this range as in this range there is no possibility for any DTMF tones. Thus audio frequency correctly fed-back to telephone line without detected by DTMF IC.
Audio beep relay turns on only after off-hook relay get activated.
I know that, in normal telephone line our vocal audio is captured by Mic, in turn converted into AF electrical signals. To check further fed-back mechanism ( & to imitate in my project), I opened my telephone set. But nothing can find out on a small, but complex circuit board inside the telephone set.
Does Anyone knows any circuits (that should be of workable) ???
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