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A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing. It is used when initiating a telephone call to transmit the destination telephone number to a telephone exchange.
On the rotary dial, the digits are arranged in a circular layout so that a finger wheel may be rotated with one finger from the position of each digit to a fixed stop position (finger stop). When released at the finger stop, the wheel returns to its home position by spring action at a speed regulated by a governor device. 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 that the telephone exchange decodes into each dialed digit. Each of the ten digits are encoded in sequences of up to ten pulses. For this reason, the method is sometimes called decadic dialling.
North American Numbering Plan
Caller ID (caller identification, CID), also called calling line identification (CLID), calling number delivery (CND), calling number identification (CNID) or calling line identification presentation (CLIP), is a telephone service, available in analog and digital phone systems and most voice over Internet Protocol (VoIP) applications, that transmits a caller's number to the called party's telephone equipment during the ringing signal, or when the call is being set up but before the call is answered. Where available, caller ID can also provide a name associated with the calling telephone number. The information made available to the called party may be displayed on a telephone's display, on a separately attached device, or personal computer.
Caller ID information typically consists of the caller's telephone number and the caller's name. A modem can pass CLID information to a computer for purposes of call logging or blocking, but this can be problematic as modems in different countries have different systems, causing hardware or software incompatibilities. However, many modems are designed and programmed to handle multiple signalling methods, and can be configured to use the local standard.
The North American Numbering Plan (NANP) is an integrated telephone numbering plan that encompasses 25 countries and territories primarily in North America, the Caribbean, and U.S. territories.
The NANP is a standardized system of numbering plan areas (NPA) using telephone numbers consisting of three-digit area code, a three-digit central office code, and a four-digit station number. Through this plan, telephone calls can be directed to particular regions of the larger NANP public switched telephone network (PSTN), where they are further routed by the local networks. The NANP is administered by the North American Numbering Plan Administration (NANPA), a service operated by Neustar corporation. The international calling code for the NANP is 1. Not all North American countries participate in the NANP.
A telephone number is a unique sequence of digits assigned to each telephone subscriber station, telephone line, or since the advent of digital telephony to an electronic telephony device, such as a mobile telephone. The telephone number serves as the address to switch telephone calls using a system of destination routing. It is entered or dialed by the calling party on the originating telephone set which transmits it in the process of signaling to a telephone exchange which completes the call either to another locally connected subscriber or via the public switched telephone network (PSTN) to the called party.
The concept of using telephone numbers instead of subscriber names when connecting calls was developed and first used between 1879 and 1880 in Lowell, MA, for the purpose of ease of training new telephone operators.
A dial tone is a telephony signal used to indicate that the telephone exchange is working, has recognised an off-hook condition at the telephone, and is ready to accept a call. The tone stops when the first numeral is dialed. If no digits are forthcoming, the permanent signal procedure is invoked, often eliciting a special information tone and an Intercept message.
Pulse dialing is a signaling technology in telecommunications in which a direct current local loop circuit is interrupted according to a defined coding system for each signal transmitted, usually a digit. Each of the ten digits are encoded in sequences of up to ten pulses each. For this reason, the method is also called decadic dialling, primarily in the United Kingdom. Historically the most common device to produce such pulse trains is the rotary dial of the telephone, lending the technology another name, rotary dialing. The term loop disconnect dialing arises from its nature of interrupting the local loop circuit. The pulse repetition rate has historically been standardized based on the response time needed for electromechanical switching systems, and most telephone systems used the nominal pulse repetition of 10 pulses per second.