AVR-Chat

After having read all the posts,first some list mom duties ;)

Remember that in MOST countries it is on offence to use un approved 
equipment direct on a telco line, SOME contries (the US I think but Dave 
can correct me if I am wrong as I am not from the USA) allow you to use 
a line issolation device to make your equipment approved.

Now after having got the leagle boring stuff over with ;) as we all like 
to play and have fun (which is why I have working PABX's here with long 
loop cards (they put out -48Vdc for line drive and 75 - 90Vac at 25Hz 
for ring))

ALL phone lines work on current !!!!!!

Relays are operated by the current through them. I know modern exchanges 
are solid state, but the theory is still the same as the telco can not 
make something that is not backwards compatable.

So now we know the half the problem, the other half is how to spec the 
load resistors to draw enough current in the various phases.

I will try make a schematic later of a circuit that can detect the 
various levels of a phone line, but these days, most of it is done in 
Hybrids.

Regards,

Kat.

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