>> Repeating for the illiterate:
>> 'native' touch-tone operation was substantially cheaper for the telco
>> than was 'native' pulse dialing.
>> They retrofitted dial-to-pulse conversion on SxS switches so that they
>> could 'pre-convert' customers to touch-tone before the switch was
>> converted to native touch-tone dialing.
>> This was a "short-term" expenditure of money now, to maximize
>> "long-term" benefits. By having a significant "installed base" of
>> touch-tone users *already*in*place* when the C.O. was converted to
>> _native_touch-tone_ handling, they could get by with far fewer sets of
>> digit decoders (dial or pulse). With 'pulse' tieing up the decoders
>> for average more than five times as long as touch-tone, there _was_
>> significant benefit to be obtained. getting even 20% of the calls on
>> touch-tone, meant a _halving_ of the number of decoder elements >> required.
> What was the cost of the touch-tone oscillator for a telephone set,
> vs. the cost of a rotary dial? There were millions of telephone sets
> out there, and at the time that was introduced the phones were
> installed, owned and maintained by the telco. The cost of the
> oscillators (key pads) would be considerable expense, particularly if
> the cost was significantly higher than 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.
But the basics of the phone were just a 500 set with updated housing. All that really changed was the dial.
But then I stop and think how much effort went into making reliable rotary dials. They were probably roughly equal in cost using adjusted dollar amounts.