ADSL (Asymmetric Digital Subscriber Line):
‘A new technology that allows more date to be sent to over existing copper telephone lines (POTS). ADSL supports data rates from 1.5 to 9 mbps when receiving data (know as the downstream rate). ADSL requires a special ADSL modem. It is not currently available to the general public except in trial areas, but many believe that it will be one of the more popular choices for Internet access over the next few years’.

Analog:
A signal which can vary continuously, taking any value between certain limits. The human voice, for which the public telephone network is designed, is an analogue signal varying in frequency and volume.in distinctions between POTS and non-POTS services are speed and bandwidth. The POTS network is also called the public switched telephone network (PSTN).

E1:
Europea 1. European equivalent to T1 (but higher bandwidth). Also sometimes written as E-1.

NT:
Network Termination

PRI:(Primary Rate Interface):
The primary rate interface in ISDN is 23B + D, for the North American standard (T1), and 30B = D for the European standard (E1).

PSTN (Public Switched Telephone Network):
A series of public dial up analog telephone circuits available for voice calls, and data transmission via a modem.

QSIG:
ISDN based protocol for signalling between nodes of a private intergrated services network, allows products from different vendors to work together. A protocol based closely on internationally agreed standards for ISDN. Both QSIG and DPNSS support similar sets of features.

Signalling:
In telephony, signalling refers to the process and the standards involved in passing control information between terminal equipment on the network e.g. between a PABX and a local exchange, or between networked PABX's.

Softphone:
Software application emulating the functionality of a standard feature-rich IP phone, operating on a desktop PC platform enabling voice calls to be conducted across IP networks using the PC as an end point.

SDSL (Symmetric Digital Subscriber Line):
A new technology that allows more data to be sent over existing copper telephone lines (POTS), supporting data rates up to 3 Mbps. This works by sending digital pulses in the high frequency area of telephone wires, not used by normal voice communications, so can operate simultaneously with voice connections over the same wires. SDSL requires a special SDSL modem.

T1:
The common name for the mainly American digital 1.544 Mbps service. Also sometimes written as T-1.

TE:
Terminal Equipment side of a digital signalling scheme.

Virtual Private Network:
The ability to create a secure private virtual link through a public access network.

WAN (Wide area network):
To be distinguished from the LAN, a WAN interconnects geographically remote sites.

10 base T:
10 Mbps LAN using twisted pair connectivity ­ e.g. using standard CAT5 cables.