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Dial pulsing. An old method of signalling dialed digits on a phone line (most commonly on the local loop). Each digit is transmitted by opening the circuit that number of times; `0' is transmitted by opening the circuit 10 times (this is why it is at the end of a rotary dial). This happens at some (almost) fixed rate; pauses between digits are guaranteed by the time it takes to dial the next digit. The rate is achieved by a centrifugal friction device on the dial mechanism.

You may simulate DP on any line by tapping the cradle at the correct rate; on some switches, you'll need to tap the cradle one more time than the digit you're dialing.

DP is also the industry abbreviation for 'Director of Photography.'
The DP (AKA cinematographer) determines how each frame is cropped, the film stock used and often what appears in the frame as well. The DP is therefore more responsible for the entire look and feel of a film than the director; and, in my opinion, isn't given enough credit.
DP or "Displaced Person" was a designation given to millions of Post-WWII civilian refugees and Nazi slave laborers. The fortunes of war had left many homeless and scattered through out Europe, far from their native countries and with no form of identification. They were designated DPs and placed into DP camps to await processing. Those from nations occupied by Soviet forces were generally allowed to immigrate to North America or Palestine.

Many in the post-war generation came to use it as an insult to describe post-World War II European immigrants of Southern Europeanand Eastern European origin.

Child: Gwamma, did you see my doggie Mr Muggles?
Grandmother: I'm sure those god damn DPs who live on the other side the alley ate your dog!

Download = D = DPer

DP /D-P/ n.

  1. Data Processing. Listed here because, according to hackers, use of the term marks one immediately as a suit. See DPer.
  2. Common abbrev for Dissociated Press.

--The Jargon File version 4.3.3, ed. ESR, previously autonoded by rescdsk.

The jargon file is in the public domain.

Dial pulsing is a method of transmitting dialled digits to the telco in circumstances where you are unable or unwilling to send DTMF signals. The signal is sent by simulating the on-hook condition (breaking the loop) and restoring the off-hook condition (making the loop) a given number of times depending on the digit dialled.

In the North American standard, a pulse rate of ten pulses per second with an break/make ratio of 60% is prescribed. So, to dial a '2', the circuit must be broken for 60 milliseconds, remade for 40 milliseconds, broken for another 60 milliseconds, and then restored for at least half a second so that the telco's switching equipment can know that the digit is finished transmitting. This timing is why impatient people to try to speed up the movement of a rotary dial often have difficulty getting their calls to go through properly.

 ~21mA    __ v _   _   _   ______   ______   ______
Current  |  | | | | | | | |      | |      | |
  ~0mA __|  |_| |_| |_| |_|  ^   |_|      |_|
         Dial      ^    Interdigital
         Tone     40ms     Pause
            {   Digit 4   }      {1}      {1}

That is a reasonable approximation of the signal as it leaves the telephone. It should be noted, however, that reactive components within the loop will 'smear' the wave as it is being transmitted to the telco's switch.

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