Dear Mr. Stan Wilson,

Current loop has been around a long time (> 75 years) and is extremely reliable. It has some very good features such as transmissions up to 10,000 feet. Most of the popular circuits functions at 20 or 60 Milliamps.

I would suggest getting hold of some books at your public library and reference them. Steve Circia (Circuit Cellar magazine founder)wrote some books on the subject during the early 1980's which had circuits which worked very well.

Thank you,

Charles Bannister