Telephone Question

[AndyS]

I have a Radio Shack Duofone Telephone Amplifier System
Model 43-278

I have been unable to find a schematic for it.....

This is an "amplified telephone listening system" and has
lots of transistors, etc, on an internal circuit board.

There is no internal power source, no battery, no wall wart...
The REN is 0.08


So, my question is, where does the unit get it's power
without loading down the telephone line ???

Thanks for all informed opinions.....

 

[Edward Lee]

It's probably powered by the phone line, which is 6-8 volts off-hook.

Could be much higher, upto 48V DC. Line distance (resistance) could
drop this somewhat.