[GreenKeys] Loop Supplies

[Jack]

ZCZC

 

Everyone should have a reliable and available loop

supply for testing TTY's, etc.

 

I have been using Hammond 187C120 transformers

which can be obtained from Mouser Electronics for

around $10.00, plus shipping. This transformer outputs

120V at 100 milliamps and has a small physical

footprint. Higher current ratings come with higher

cost.

 

All you need is a diode, electrolytic filter capacitor

and a current limiting resistor and you have

a "loop supply". I use a 1N4007 diode, 40 mfd 450V

capacitor and an adjustable wirewound resistor of

approximately 2,000 Ohms for a 60 ma. loop.

 

Jack K0TTY

 

NNNN

 

 

 

 

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