27-06-2012, 12:26 PM
Touch Tone Telephone Pads
[attachment=25713]
Dial phones became popular quickly
The rotary dial came along much later. You could dial a 4 digit number yourself. Long distance required an operator.
Dial phones created pulses on the phone line. A two pulsed the line two times.
DTMF
Dual Tone Multi-Frequency
Pressing a key generates two frequencies or sine waves
These range from 770 Hz to 1633 Hz
Transistorized circuitry both sends and receives these tones
Whoops! A, B, C, D ?
This system shows 16 keys , there are only 12 on a regular phone !
Operators have the extra keys…
These are for: Flash Override, Flash, Immediate, and Priority
They have to do with long distance signaling.
[attachment=25713]
Dial phones became popular quickly
The rotary dial came along much later. You could dial a 4 digit number yourself. Long distance required an operator.
Dial phones created pulses on the phone line. A two pulsed the line two times.
DTMF
Dual Tone Multi-Frequency
Pressing a key generates two frequencies or sine waves
These range from 770 Hz to 1633 Hz
Transistorized circuitry both sends and receives these tones
Whoops! A, B, C, D ?
This system shows 16 keys , there are only 12 on a regular phone !
Operators have the extra keys…
These are for: Flash Override, Flash, Immediate, and Priority
They have to do with long distance signaling.