Business telecommunications and IT systems

i) Per Annum. Annual.

ii) Public Address.

Private Automatic Branch Exchange. One of thress types of telephone system designed for businesses.

The design is such that incoming telephone calls appear at a switchboard to be answered by a recptionist before being transferred the appropita extension.

Extensions are maily POTs.

see Keyphone System and ACD System.

A formatted unit of data.

When data is formatted into packets, the bitrate of the communication medium can be better shared among users than if the network were circuit switched.

By using packet switched networking it is also harder to guarantee a lowest possible bitrate.

see Datagram.

Packet over SONET/SDH (POS) is a communications protocol for transmitting packets in the form of the Point to Point Protocol (PPP) over SDH or SONET, which are both standard protocols for communicating digital information using lasers or light emitting diodes (LEDs) over optical fibre at high line rates.

POS is defined as PPP over SONET/SDH.

PPP is the Point to Point Protocol that was designed as a standard method of communicating over point-to-point links.

A packet-switched network is a digital communications network that groups all transmitted data, irrespective of content, type, or structure into suitably-sized blocks, called packets.

The network over which packets are transmitted is a shared network which routes each packet independently from all others and allocates transmission resources as needed.

The technique of switching data in a network where individual blocks or packets of data of controlled size and format are accepted by the network and routed to their destination.

The sequence is maintained and the destination is determined by exchanging control packets between the originating terminal and the network before transfer starts.

see PSDN.

Packet Assembler / Disassembler.

A device used in an X.25 network to permit terminals which do not have an interface suitable for direct connection to a packet switched network to access such a network.

Password Authentication Procedure.

A procedure used to validate a connection request.

After the link is established, the requestor sends a password and an ID to the server. The server either validates the request and sends back an acknowledgement, terminates the connection, or offers the requestor another chance.

A port which sends data at 8 bits at a time, in parallel.

Therefore faster than a serial port.

Typically used to connect a computer to a printer.

see Daughter Extension.

A technique of error detection in which one bit is added to each data character so that the number of logic one bits per character is always even, or always odd, or always a mark condition, or always a space condition.

Memory that has an extra bit, dedicated to checking for errors.

see Non-parity Memory and Parity Checking.

see S0-bus.

A short lead used to connect one patch panel to another.

To differentiate between signal types, red would typically be used for voice and blue for data.

The leads usually have male (RJ45) plugs at each end.

Also known as a Fly Lead.

A patch panel is a cable connection system.

Various ports of a piece of equipment (such as the extension ports of a telephone system) would be cabled to the rear of a patch panel.

In this example, another patch panel would have office extension outlets cabled to its rear.

Short patch leads could be used to link extensions of the telephone system to extension outlets within the office.

This type of connection allows for flexibility in moving the location of extensions around a building.

Path Vector Protocol is a computer network routing protocol which maintains the path information that gets updated dynamically.

Path vector protocols are a class of Distance Vector Protocol in contrast to Link State Protocol.

Private Branch Exchange.

The generic term given to a telephone system on a customer's premises.

i)  Personal Computer. A PC can be used on its own or connected to a network, such as a LAN. Not easily portable.

ii)  Private Circuit.

PC Card is a more recent name for the PCMCIA card.

IBM's version of DOS, derived from Microsoft's DOS.