I have about a dozen of them as well. The ones with low traffic no problems. The ones with high pots traffic...I said six, but it has been five failures. Two offices failed twice, one of those the replacement system lasted one week. I have never found out what the problem was, but it looked like a power supply issue to me.

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"Old phone guys never die, they just get locked in some closet with an old phone system and forgotten about"

Retired, taking photographs and hoping to fly one of my many kites.