Nowadays, the physical destination corresponding to a particular address is stored in a computer database. To provide new network addresses, area codes were split and overlaid, and a user in these locations needs to dial ten digits. Today, telephone numbers are in the form NXX-NXX-XXXX, and the area code no longer corresponds to a unique geographic area, nor does it necessarily mean long distance charges apply. The last area code was allocated with this scheme in the 1990s. With the introduction of computer-based switches, computer control systems for switching, and the need for more network addresses, all of this was changed. Users had to dial between ﬁve and ten digits, sometimes prefaced with a 1 to indicate the desired destination.

Last four digits – the physical pair of wires.

The groups of digits were designated as follows: Restrictions were placed on the values of various digits so that analog and mechanical switches could distinguish between them.Īddresses were originally of the form NBN-NNX-XXXX, where Previously, the North American Numbering Plan for telephone numbers consisted of digits, each with a speciﬁc purpose.

the number of digits that must be dialed, and how an address is assigned to a subscriber is called a dialing or numbering plan. For POTS, the network address is called a telephone number.

Generally, the network address is the piece of information that identifies the ﬁnal destination of the connection in a network. When a request to communicate has been acknowledged with a dial tone, the network needs to be told where the call is to be connected to. In this article, we are delving deeper into POTS, and we’ll cover such topics as Dialing Plan, Address Signaling, Pulse Dialing, Touch Tone or DTMF, In-Band Signaling, Hidden Buttons and Caller ID In our previous article, Everything you need to know about POTS (Plain Ordinary Telephone Service) and Analogue Phone Systems – Master 101 class we looked at the basics of POTS telephone systems, such as Tip & Ring, Twisted Pair, Balanced Signalling, and Call Progress Tones.

Dtmf tone dialer