From: smb%ulysses.btl.csnet@CSNET-RELAY.ARPA
Date: Mon, 11 Nov 1985  08:01:09
Subject: Re:  TELECOM Digest V5 #64

	Date: Sat, 9 Nov 85 13:55:47 PST
	From: ihnp4!kitty!larry@ucbvax.berkeley.edu
	Subject: Re: Rochester telephone service
	
		Dialing speed (rotary (DP) or DTMF, no matter which)
	has absolutely NO effect on call completion success, the only
	exception being if your dialed digits are too slow or too fast
	for detection (i.e., < 6 || > 15 pps DP or > 10 digits/sec
	DTMF).  If you are in a crossbar office, you are effectively
	"offline" when dialing; your dialed digits are being decoded
	and stored in an `originating register' (OR).  Only when the OR
	detects the completion of a dialing sequence (or abort of same
	through a timeout) is the call routed to the `marker' for route
	section and transmission through the DDD network.

Umm -- that's not always the case.  When I lived in Durham, for example
(1972-1977), it most certainly was important.  (Durham is served by
GTE.)  You could hear the DTMF->pulse conversion going on as you dialed
-- go too fast and you'd confuse the switch.  This may, of course, have
been an antiquted switch; they didn't install automatic number
identification equipment until about 1974 or 1975, and then only under
orders from the Utilities Commission.  Chapel Hill was even worse until
Southern Bell bought the phone company from the University (1978) and
replaced the old step exchange with an ESS (1981).  One learned to
listen to the click pattern as one dialed (rotary only, of course); the
wrong pattern of clicks meant you wouldn't get through.  (Have you ever
tried to exlain to a repair service clerk that you wanted to report a
problem with a bouncing relay on some trunk group, which you currently
had seized, rather than with some particular number?)  Once I was using
an autodialer to call the local Comp Center, on 933-9911.  The switch
gave up after the first 3 or 4 digits and gave me a new dial tone in
time for the fifth digit.  So I ended up dialing 911...

		--Steve Bellovin
		AT&T Bell Laboratories

Anything I say here is my own opinions, not company policy, etc.