Whilst most push button phones contain electronics to enable them emulate LD (Loop Disconnect) technology by generating trains of pulses, almost universally, push button phones use a system called DTMF.ĭTMF or Dual-Tone Multi-Frequence, are the tones generated when you press keys on a numeric keypad. This created a train of short pulses (affectionately know as 'clicks'), and sequences of these click trains (with short gaps in-between) was the mechanism used to encode the desired number.Īfter rotary dials, phones moved on to using push buttons. For every digit position that the disk rotated backwards an electrical circuit was momentarily broken and then made again. The finger was then removed and the spring would return the dial back to the mean position at a damped uniform angular speed. To select a number, a finger was placed in the corresponding hole of the dial, and then the dial was manual rotated clockwise (against a torsion spring) until the finger pressed against an end stop. This process is given the name "Loop Disconnect". Old technology phones used to dial numbers through a series of pulses. The vernacular goes even further back! We still "Hang up" when we want to terminate a call, and this refers to the action of placing the receiver back onto the hook of a phone that was shaped like a candlestick! Interestingly, we still use the verb "Dial" to describe the action we perform when we use a phone to make an outgoing call, even though modern phones do not have dials!Īlso a phone still "rings" when it needs answering, even though it does not have a bell inside. For details of the other criteria and decisions refer to the article. In my blog posting I'm going to summarize just the results the key arrangements. The outcome of this research project and testing is the keypad we know today. This classical piece of research covers four aspects of the keypad design: Key arrangement, Force displacement characteristics, Button top design, and Central office factors. You can download a copy of the article here. The article was entitled: Human Factors Engineering Studies of the Design and Use of Pushbutton Telephone Sets. A summary of this work was published in the July 1960 edition of the Bell Systems Technical Journal. I strongly encourage you, if you have time, to read their entire publication on the subject. The answers to these questions can be found in a fascinating piece of research performed by AT&T in 1960. Why are they arranged in a 3x3 grid with the zero below? How did this layout become a standard? Why is this layout subtly different to the way the numbers are arranged on a calculator or numeric keypad? What other layouts were considered? “Why are the numbers on a telephone keypad arranged the way they are?” Have you ever thought "Why are the numbers on a telephone keypad arranged the way they are?"
0 Comments
Leave a Reply. |