Re: History -- why not 20 pulse/sec dials? [telecom]

Re: History -- why not 20 pulse/sec dials? [telecom]
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Subject Author Date
Re: History -- why not 20 pulse/sec dials? [telecom] Sam Spade 08-07-2008
Posted by Sam Spade on August 7, 2008, 9:11 pm
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>From Sam Spade:

Geoffrey Welsh wrote:
>
> If I recall correctly, at one point I owned a modem with hook control but not
> touch-tone... dialling was accomplished by setting and clearing a bit on an
> I/O port under program control. I don't know how much a DTMF generator would
> have added to the cost of the modem, but we really didn't need it either.
> And, yes, many terminal programs offered to dial faster than 10 PPS.
>

Makes me think of all the money I wasted on
the ever-better Hayes modems before the
Internet became ubiquitous.

I don't recall the specifics of the register
setting, but you could make the later Hayes
spit out the DTMF string really fast. The
DTMF orgination hoppers (or whatever they're
called) on my local DMS-100 could correctly
process the rapid fire stuff until it was
set so fast it sounded like a blur. I doubt
those DMTF readers on a SxS office would
have done quite as well.






Posted by David Clayton on August 8, 2008, 1:12 pm
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On Thu, 07 Aug 2008 21:11:58 -0400, Sam Spade wrote:
......
> I don't recall the specifics of the register setting, but you could make
> the later Hayes spit out the DTMF string really fast. The DTMF
> orgination hoppers (or whatever they're called) on my local DMS-100
> could correctly process the rapid fire stuff until it was set so fast it
> sounded like a blur. I doubt those DMTF readers on a SxS office would
> have done quite as well.

The major problem with rapid DTMF is the gap between identical digits -
if the receiving end setup needed a decent time to discriminate between
two separate identical tone pairs (rather than guess it was one digit
with an interruption) then you could get into all sorts of trouble.

I ran into this with voice mail systems with in-band signalling for
Message Waiting indicators, you could tweak the DTMF send rate and think
that you had a system functioning "better" than the default settings -
but then be hammered by support calls by people saying that they don't
get reliable MW while other users have no problem at all, and then
eventually figure out that *all* the problem users have a pair of
identical digits in their extension numbers...... :-(

--
Regards, David.

David Clayton
Melbourne, Victoria, Australia.

Knowledge is a measure of how many answers you have, intelligence is a
measure of how many questions you have.


Posted by Robert Bonomi on August 9, 2008, 12:04 pm
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>>From Sam Spade:
>
>Geoffrey Welsh wrote:
>>
>> If I recall correctly, at one point I owned a modem with hook control but not
>> touch-tone... dialling was accomplished by setting and clearing a bit on an
>> I/O port under program control. I don't know how much a DTMF generator would
>> have added to the cost of the modem, but we really didn't need it either.
>> And, yes, many terminal programs offered to dial faster than 10 PPS.
>>
>
>Makes me think of all the money I wasted on
>the ever-better Hayes modems before the
>Internet became ubiquitous.
>
>I don't recall the specifics of the register
>setting, but you could make the later Hayes
>spit out the DTMF string really fast.

I don't remembe the register number either, but you used it to specify,
in milliseconds, the duation of the tone burst _and_ the inter-digit delay.
Default setting ws '70', which dialed a local (7-digit) number in almost
exactly 1 second.

Minimum value the genuine Hayes would accept was 20, which was shorter than
most COs would recognize _accurately_. A setting of 35 generally worked
on in-town lines.


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other useful resources:
The Federal Communications Commission (FCC)
Telecommunications Industry Association
Electronic and Software Security Products and Services
International Telecommunication Union

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