Re: [microsound] telephone numeric keypad tones?

[vze26m98 <vze26m98@xxxxxxxxxxxxx>]

If you searched the web, you could find a bunch of information I'm sure,
or likely there's someone here that has it all memorized, but here's
some rough answers:


On 1/4/04 at 3:19 PM, graham miller <grahammiller@xxxxxxxxxxxx> wrote:

> why the previous rotary system?

The rotary system interrupts the current loop on your phone line for,
say, 4 or 9 times when you dial that number. It was a crude but easy to
detect system.

> i was wondering if there was any kind of history to these tones?
> when did the system come into place?

Tone signaling came into being when computers started to become more
important to telephone switching, or when computers BECAME telephone
switches. Sending large numbers of current fluctuations through the
phone network wasn't real great, the current signal became lost (or had
to be regenerated) within the switching system and there was the extra
hardware cost of buffers and converters.

> does the system have an actual name?

DTMF. for Dual Tone Multi Frequency

> an inventor? who set the pitches? why these pitches?

I would guess AT&T or a consortium of phone companies standardizing an
AT&T invented system. The pitches are probably close to vocal bandwidth
so that they would survive all the compression, etc. of the phone
system.

Best,

Tad


<tad@xxxxxxxxxxxxxxxxxxx>

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