Hello All,



A prelude to my last post about Ac signals and a problem with detecting
an off hook if I can't get this condition detected without the dc
component of the signal. How can I add the dc component, even if it's
only 12vdc instead of the regular 48vdc the Telco uses so that I can use
it to detect an off hook condition. I'm detecting this condition in a
closed loop off a relay that is not connected to the telephone company
it is a ringing signal that I have created on my circuit that does not
have the dc component, unfortunately this does not give me a way to
detect an off hook. A bridge rectification of my ringing signal gives me
41dc during ringing and 14vd off-hook but the ring cadence would be a
problem as it would provide a false reset signal during ringing silence
between ringing pulses and the dc voltages are too high. The bridge
rectifier also seems to load the ringer circuit down a little too much.
So my next thought is to add enough dc to the loop to detect the off
hook and get a good logic high or low that is independent of the
ringing, I am not sure how to add dc to the ac without blowing the thing
up.



Any ideas?



Steve

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