Indicator phone line in use

01:03:51

published 11 years ago

jeffers

11 years ago

When the green LED lights indicates that the line is free and can be used. happens when the circuit receives 48VDC delivering the telephone exchange.In turn, the red LED lights up when the line is being occupied by another person in a different extension to ours.This happens because when you lift the handset from another extension, the line voltage drops below the 7vcd

hurz

11 years ago

And dont draw to much current in green mode or your line is busy forever. You took 1mA LEDs which might be low enough

hurz

11 years ago

BTW, an incoming call might be autoanswered because green gets more than 2mA current. Ring voltage is 25Hz 90V peak

faceblast

11 years ago

Be careful screwing around with the phone line, there are some pretty heavy laws around that. All devices have to be line isolated. If the port is loaded while not engaged to call it'll shut down for protection and a relectogram up one side of the pair to show the line has suddenly doubled in length, so they'll know instantly that you're screwing with it

jeffers

11 years ago

Thanks guys

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