>> What was the cost of the touch-tone oscillator for a telephone set,
>> vs. the cost of a rotary dial?
> Considering that a rotary dial was nothing but springs and gears,
> while a DTMF pad had coils (Bell loved those ferrous cup cores!),
> resistors, transistors, specially plated contacts, etc.
It is hard for us to believe today, but it took a very long time for
the price of electronics to come down far enough to be cheaper than
equivalent mechanical devices.
In 1965 some consumer electronic things like radios, tape recorders,
and TV sets still used some vacuum tubes because they were still
cheapter than transistors at that point in time.
So, stamping out and assembling springs and gears was cheaper than
making and assembling transistors for a Touch Tone pad in those years.
All components were discrete in those days.
As mentioned, in another thread it was stated that it was cheaper to
do many pre-processing steps on electro-mechanical gear than in the
electronic CPU because the CPU was so damn expensive compared to the
EAM gear. Most computer centers of that era had EAM gear on standby
to do supplemental tasks like card sorting or card deck printing
rather than have the expensive computer do it. Further, it was even
cheaper despite the cost of paying a person to run the EAM machine
instead of the automatic computer.
While others claim Touch Tone saved the phone company money, I still
assert it was more expensive for them, esp in non-common- control
offices. I don't think tone interpreters for common- control offices
were that cheap either.
I note that PBX operators had 20 pps dials while the rest of us had 10
pps. Some kids experimented and found 20 pps worked at home. Now, it
was easy to modify the dial to go faster -- so why didn't Bell have
everyone at 20 pps -- faster utilization of equipment? I strongly
suspect there were valid technical reasons not to.
Indeed, from what I recall from Bell Labs Record, it took quite some
time (well into the 1970s) that Bell equipment could really make good
use of fast dialing. Eventually they would start interpreting digits
as they came in and begin route set up before the whole number was
[TELECOM Digest Editor's Note: I had a couple of Hayes Modems which
could be switched between pulse and tone dialing, and you could set
the 'speed' of the pulsing or the 'speed' of the tone signals. You
could make both modes go quite fast; with tone dialing so fast that
it was little more than just a single blip in your ear, and most
times it would work quite well. Only on occassion the modem would
give its short little blip or tone burst when dialing *before* the
line was set up to allow it, and you would have to redial, but
usually it worked okay. PAT]