Rotary dial

dialrotary telephonerotary phonetelephone dialrotaryrotary phonesdialsrotary telephone dial rotary dial telephone exchangesBakelite telephones
A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing.wikipedia
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Telephone

phonetelephonesLocal Telephone Service
A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing.
Until the 1960s dials used almost exclusively the rotary technology, which was replaced by dual-tone multi-frequency signaling (DTMF) with pushbutton telephones (A4).

Pulse dialing

dial pulsepulse diallingpulse dial
A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing.
Historically, the most common device to produce such pulse trains is the rotary dial of the telephone, lending the technology another name, rotary dialing.

Push-button telephone

10- or 12-button touch-tone telephonespush-buttonpush-button dialing
From the 1980s onward, the rotary dial was gradually supplanted by dual-tone multi-frequency push-button dialing, first introduced to the public at the 1962 World's Fair under the trade name "Touch-Tone".
The push-button telephone is a telephone that has buttons or keys for dialing a telephone number, in contrast to having a rotary dial as in earlier telephone instruments.

Dual-tone multi-frequency signaling

DTMFtouch-tonetouch tone
From the 1980s onward, the rotary dial was gradually supplanted by dual-tone multi-frequency push-button dialing, first introduced to the public at the 1962 World's Fair under the trade name "Touch-Tone".
The Touch-Tone system using a telephone keypad gradually replaced the use of rotary dial and has become the industry standard for landline and mobile service.

Telephone keypad

keypad12-key telephone keypaddial pad
Touch-tone technology primarily used a keypad in form of a rectangular array of push-buttons for dialing.
It was standardized when the dual-tone multi-frequency signaling (DTMF) system was developed in the Bell System in the United States in the 1960s that replaced rotary dialing originally developed in electromechanical switching systems.

Signaling (telecommunications)

signalsignalingsignalling
A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing.
In the first half of the 20th century, addressing formation is done by using a rotary dial, which rapidly breaks the line current into pulses, with the number of pulses conveying the address.

Telephone exchange

exchangescentral officeexchange
It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange.
When used with a rotary telephone dial, each pair of digits caused the shaft of the central contact "hand" of the stepping switch to first step (ratchet) up one level for each pulse in the first digit and then to swing horizontally in a contact row with one small rotation for each pulse in the next digit.

Telephone call

callphone callphone calls
It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange.
The caller then rotary dials or presses buttons for the phone number needed to complete the call, and the call is routed to the phone which has that number.

North American Numbering Plan

Area codeArea codesArea code(s)
On rotary dial phones smaller numbers, such as 2, are dialed more rapidly than longer numbers, such as 9 (because the dial turns much further with a 9). In 1947, area codes were introduced in the United States, so as to facilitate direct distance dialing first by operators, then by subscribers.
The codes prefixed with an asterisk symbol are intended for use on Touch-Tone telephones, whereas the four-digit numbers prefixed 11xx are intended for use on rotary dial telephones, where the Touch-Tone * symbol is not available.

Almon Brown Strowger

Almon B. StrowgerStrowger
The first patent for a rotary dial was granted to Almon Brown Strowger (November 29, 1892) as, but the commonly known form with holes in the finger wheel was not introduced until ca. 1904.
Rotary dial

Panel switch

panelother exchange typespanel dial systems
Hence the first Panel automatic exchanges cutover in 1915 in Newark, New Jersey used "semiautomatic" operation with the local operator keying the number for the caller.
While the Strowger (step-by-step) switch moved under direct control of dial pulses that came from the telephone dial, the more sophisticated Panel switch had senders, which registered and stored the digits that the customer dialed, and then translated the received digits into numbers appropriate to drive the selectors to their desired position: District Brush, District Group, Office Brush, Office Group, Incoming Brush, Incoming Group, Final Brush, Final Tens, Final Units.

999 (emergency telephone number)

9999-9-9999 call
A relic of these differences is found in emergency telephone numbers used in various countries; the United Kingdom selected 999 due to the ease of converting call office dials to make free calls.
The 9-9-9 format was chosen based on the 'button A' and 'button B' design of pre-payment coin-operated public payphones in wide use (first introduced in 1925) which could be easily modified to allow free use of the 9 digit on the rotary dial in addition to the 0 digit (then used to call the operator), without allowing free use of numbers involving other digits; other combinations of free call 9 and 0 were later used for more purposes, including multiples of 9 (to access exchanges before STD came into use) as a fail-safe for attempted emergency calls, e.g. 9 or 99, reaching at least an operator.

Dial tone

dial-tonedialling tonestutter dial tone
Dial tone
When he picked up his own household phone his assistant had to explain what the strange noise was, as well as show Eisenhower how to use a rotary dial phone.

All-figure dialling

all figure dialling01609All Figure Numbering
Dials outside Canada, the United States, and large cities in Britain (before all-figure dialling) usually did not bear alphabetic characters or an indication of the word "operator" in addition to numbers.
The rotary dial included the corresponding letters next to the appropriate digits.

Single-frequency signaling

SF tonesingle frequencysingle frequency tones
Single-frequency signaling
In the seized state, dial pulses are conveyed by bursts of SF tone, corresponding to the interruptions in dc continuity created by a rotary dial or other DC dialing mechanism.

History of the telephone

telephonemechanical telephonetelephone history
History of the telephone
The rotary dial in the base interrupted the line current by repeatedly but very briefly disconnecting the line 1 to 10 times for each digit, and the hook switch (in the center of the circuit diagram) permanently disconnected the line and the transmitter battery while the handset was on the cradle.

Stepping switch

uniselectoruniselectorsstepping relay
Stepping switch
The coils were typically driven by the electrical pulses derived from a rotary telephone dial.

Telephone switchboard

switchboardswitchboardscentral switchboard
A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing.

Telecommunication

telecommunicationscommunicationstelecom
A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing.

Governor (device)

governorspeed governorgovernors
When released at the finger stop, the wheel returns to its home position by spring action at a speed regulated by a governor device.

Local loop

subscriber lineloopsubscriber loop
During this return rotation, the dial interrupts the direct electrical current of the telephone line (local loop) a specific number of times for each digit and thereby generates electrical pulses which the telephone exchange decodes into each dialed digit.

Pulse (signal processing)

pulsepulsespulsing
During this return rotation, the dial interrupts the direct electrical current of the telephone line (local loop) a specific number of times for each digit and thereby generates electrical pulses which the telephone exchange decodes into each dialed digit.

Bell System

BellBell Operating CompaniesBell Telephone
While used in telephone systems of the independent telephone companies, rotary dial service in the Bell System in the United States was not common until the introduction of the Western Electric model 50AL in 1919.

Century 21 Exposition

1962 World's FairSeattle World's Fair1962 Seattle World's Fair
From the 1980s onward, the rotary dial was gradually supplanted by dual-tone multi-frequency push-button dialing, first introduced to the public at the 1962 World's Fair under the trade name "Touch-Tone".

Telegraphy

telegraphtelegramcable
From as early as 1836 onward, various suggestions and inventions of dials for sending telegraph signals were reported.