TELECOM Digest OnLine - Sorted: Re: Speed Dials

Re: Speed Dials

Mr Joseph Singer (
Tue, 12 Sep 2006 11:51:57 PDT 11 Sep 2006 07:24:53 -0700 wrote:

> The dial speed is about 10 pulses per second. (A good modem manual
> will tell you exactly the "contact make/break" times and the settings
> for outside the U.S. as well).

> Anyway, I believe panel switching and certainly crossbar and ESS could
> and would accept 20 pulses per second. Way back in HS a kid figured
> out on his phone dial an adjustment to make it 20 p/s and it worked
> (on either #1 xbar or panel). PBX switchboards had 20 p/s dials.

> However, I think they realized this higher speed was rough on
> equipment and did not provide it to the general public for that
> reason.

Personally, I don't believe it caused any more wear and tear on
equipment than what a 10 pps dial would make on the system. Since
panel, #1XB and #5XB all used common control and didn't do anything
til the requisite amount of digits had been entered in the receiving
registers likely could care less how fast the pulses came into the
registers. And I don't think it caused any more wear and tear than
receiving MF or DTMF.

> I don't know if SxS could handle it but SxS components had
> wear issues and certain improvements was rough on SxS unless it was
> carefully spread out among switches within an office.

Wear issues weren't likely the problem with 20 pps dials o n SXS. The
problem is that SXS systems cannot keep up with pulses as fast as 20
pps. It might work *sometimes* but for constant reliable service 20
pps dials would not likely have enough reliability to be used.

As for "why subscribers were never given 20 pps dial phones as a usual
thing" my guess is that WECO never put that into widespread production
so it wasn't made available as a standard dial in a standard 302 or
500 (whichever would have been in use at the time.) When Touch-Tone
(DTMF) came out in '64 it was a viable option that was going to
eventually be implemented throughout the Bell System eventually.
Whether this is the reason or not is only my speculation.

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