Every CO (at least in NYC and all of GTE) had their own Milliwatt tone. The idea was that you could test the loss on every line in the exchange.
Programming a line for MWT meant that when you dialed into it, it put out a 1004hz tone at 0.0db. You hooked your test set (not a butt set!) to the circuit (at the subscriber end) and read what the loss was.
As I recall -2.5db was optimal and -5.0 was the outside, though some circuits were much worse. Of course you should always read 1004 hz. If you didn't, then the circuit was hosed- big time.
Whenever we got a leased line (CSV circuit) from NY Tel we would test it to see if it met the parameters we were paying for.
Nowadays, I think it's just used for identifying circuits. I don't remember the last time I saw a tech with an analog transmission
test set.
There was also a "silent tone" line, You dialed into it, got 5 seconds of milliwatt and then it went dead quiet. It was perfect for troubleshooting noisy, staticy lines.
Sam
