One of our Network Administrators was having periodic troubles with a T1 in our Dallas branch.

After several months with him going back and forth with the service provider, he had a third party come out and look at it.

An hour and a half later, we get a bill explaining they punched down a disconnected wire.

Can a 4-wire T1 even run on 3 wires?

Thanks, in advance.

No

No is correct, but if it is working fine now, the connection could have been poor one rather than fully loose. The proof will be in the pudding.

I beg to differ! I am guilty of exactly what was described! I made up a 60' cable to go from the "smartjack" to the Mitel 021 T1 card in an SX200D and landed the transmit one pin off. It worked just fine for several months and then, for no reason at all, Red ! It would still intermittently work for an hour or more at a time! Took me 2 days to find the 'error in my ways'. I know the answer should be no, but........

I agree. I have encountered several instances where a T1 will function (though with many errors) with one half of the transmit or receive pair open.

With that being said, it is possible for a circuit to function under these circumstances, the truth is that if it does, it will give you nothing but trouble. I'd be willing to bet that your problem actually was a case of this.

Beware of some pricey punch tools that are a bit too roomy. They can allow the wire to sort of fold over the pin rather than going fully into the pin. The insulation does get cut, but there is too little force on the copper to produce a good bond. Intermittent failure will eventually result.

Tony N