« Please Support Joybbubles, a Documentary About Joe Engressia | Main | Bill Acker, 1953-2015 »

December 15, 2014


Frank Carson

Understand some of the Jerry Lewis MDA Telethons in the '70s-early 80s also used No5 crossbar ACD for handling incoming calls. Same test mode with the 'D' key, etc.

Account Deleted

Nitpick: The AUTOVON levels were Flash Override, Flash, Immediate, and Priority, from A to D. Routine calls were dialed without a precedence level.

Phil Lapsley

Wow. Brain fade. Good catch, Todd, corrected!

Phone Trips (Mark Bernay)

This was a long time ago so I'm not sure, but I remember several details differently. First, I think you could press any of the A,B,C,or D keys as the call was going through, it didn't have to be D.

Second, you had to be HOLDING DOWN the key at the INSTANT the operator answered, you couldn't just press it once while it was ringing. So when you heard the ringing start, you would press and hold a key, then listen really carefully through the loud touchtone and you could barely hear the click of the operator answering, then you could let the key up.

Third, I think this was discovered by a guy named Sterling in Seattle, not Bob or Chris Bernay. I kind of remember Sterling telling me about this and thinking how weird it was that he was able to stumble across something like this.


The Bell System Practice that describes the ACD test arrangement is here:


For those interested in details of how Ma Bell equipped the ACD test function.

The comments to this entry are closed.

Just Released in Paperback

The definitive history of the phone phreaks, available in hardback, paperback, and ebook forms from Amazon | Barnes & Noble | IndieBound | Books-A-Million or wherever fine books are sold.