Glossary of Terms PSTN
Produced by Adept Telecom for COMMS INTEGRATOR L&C Asset Group
Glossary of Terms
Ever been confused by all the telecoms jargon? This quick reference guide will help you through the diagrams and phrases
Carrier Pre-Selection Carrier Pre-Selection (CPS) is a mechanism that allows end-users to select, in advance, alternative Communications Providers to carry their calls without having to dial a prefix or install any special equipment at their premises. The end-user subscribes to the services of one or more CPS operators (CPSOs) and chooses the type of calls (e.g. all national calls) to be carried by them. The end-user may have a direct retail relationship with the CPSO, or may purchase the service via a CPS Reseller. The end-user is billed for these calls by the CPSO or CPS Reseller. Wholesale Line Rental Wholesale line rental (WLR) is a product that BT is obliged to provide to other Communications Providers. It enables other Communications Providers to offer both line rental and calls to end-users over BT's local network. This usually means that the end-user no longer has a contractual relationship with BT and is billed solely by the WLR Provider PBX/PABX Short for private branch exchange, a PBX is a private telephone network used within a company. Users of the PBX share a certain number of outside lines for making telephone calls external to the PBX. IP PBX - IP-based Private Branch Exchange Telephone system using VoIP technology to distribute devices and telephones. Most medium-sized and larger companies use a PBX because it's less expensive than connecting an external telephone line to every telephone in the organization. In addition, it's easier to call someone within a PBX because the number you need to dial is typically just 3 or 4 digits. PSTN Stands for Public Switched Telephone Network. In other words, a bog-standard domestic phone line. Only allows you to have one phone conversation over it at a time, but you can run ADSL broadband over it, (but not SDSL). The next level up from PSTN is ISDN DDI - Direct Dialling Inwards / Direct Dialling Inbound DDI numbers are applied to ISDN lines, allowing selected staff, services and departments to have direct-dial facilities. CLI - Calling Line Identity The inbound callerâ€™s telephone number. Associated as a phone feature mainly with ISDN lines, however also presented over mobile and SIP Trunk networks. DTMF DTMF means - dual tone multi frequency. This is also known as Touch Tone. It is a method, used by the telephone system to communicate the pressed keys when dialling. DTMF allows navigation of voice menus and other advanced calling services. 20CN -20th Century Network 21CN - 21st Century Network BT's next generation network which is being rolled out between 2007 and 2012. ADSL - Asymmetric Digital Subscriber Line This is the most common way in which broadband is delivered in the UK. ADSl2+ - Asymmetric Digital Subscriber Line, version 2+ A form of ADSL offering up to 24Mbps downloads, and up to 2.5Mbps upstream (for the Annex M version). SDSL - Symmetric Digital Subscriber Line DSL is a service in which the upstream and downstream channels operate at the same speed. DSL Symmetric digital subscriber line. In plain English, a way to access the internet using a conventional phone line. Symmetric means that upload speeds and download speeds are the same. SDSL is a lot faster and more expensive than ADSL.Another difference between ADSL and SDSL is that SDSL cannot share a phone line with a telephone - it needs its own
Contention ratio The 'contention ratio' of an ADSL connection means the maximum number of organisations that share that connection. It's quite normal for domestic ADSL to offer contention ratios of 50:1. So you could be sharing your connection to the internet with up to 49 other houses at any one time. Commercial ADSL tends to be more expensive than domestic, but typically offers better contention ratios at around 20:1. If you're not getting the speed you expect it can be due to the contention ratio. But it could be down to many other factors such as the capacity of the website you are accessing, or the quality of your phone line and the distance you are from the local BT exchange FTTC - Fibre To The Cabinet The process by which fibre optic cables are laid from the exchange to the cabinet (typically a green street cabinet). Traditional copper connections then run from the street cabinet to the premises.
FTTP - Fibre To The Premises Fibre optic cables delivering services directly to the premises from a local POP or telephone exchange. IP - Internet Protocol The most commonly used set of rules governing how information is sent over networks (not necessarily just the Internet). ISDN - Integrated Services Digital Network A means of transmitting voice and data at up to 64kbps per channel. SDSL - Symmetric Digital Subscriber Line DSL is a service in which the upstream and downstream channels operate at the same speed.
DASS - Digital Associated Signaling System DASS is the old UK-based standard for ISDN30 installations. Many businesses still use ISDN30 with the DASS protocol, which will need to be upgraded to ISDN30E before a new telephone system can be installed. DASS is identified by the co-axial type connectors used on the NTE box NTE - Network Termination Equipment The NTE is the connection box for ISDN30 and other network services using ISDN protocols (e.g. megastreams and MPLS services). An NTE can support up to 4 bearers, or trunks, of ISDN30 (i.e. up to 120 phone lines). The ISDN30E connections are identified by RJ45 connections. NTEs supporting older DASS-type protocols have co-axial connections. ISP - Internet Service Provider A provider of internet access services (such as ADSL). LLU - Local Loop Unbundling The BT Openreach product that allows ISPs to install their own equipment in telephone exchanges and just use the copper pair to premises. QoS - Quality of Service A measure of how "good" the service on a broadband connection is. Most QoS implementations allow you to define different priorities for different types of traffic (e.g. Web, VoIP, email) PoE - Power over Ethernet VoIP telephones require electrical power. This power is usually provided by your Ethernet switch (known as a PoE Switch), which powers the telephone as well as delivering the VoIP phone call data to it. If you donâ€™t have PoE Switches, you will need mains power adaptors for each telephone, with an associated power outlet at the Workstation.
VoIP - Voice over IP The generic name given to telephony services that communicates using IP rather than the old PSTN.
Hosted Solution VoIP telephone system that is hosted by a 3rd party from a remote location. Telephones connect via the internet to the main system and all services are rented on a per-user/per telephone basis. Usually not financially viable for large businesses. Convergence The use of a basic telephone on the desk, with a desktop PC providing telecoms functions via a dedicated software application. Calls are transferred using the mouse/keyboard.
NTE - Network Termination Equipment The NTE is the connection box for ISDN30 and other network services using ISDN protocols (e.g. megastreams and MPLS services). An NTE can support up to 4 bearers, or trunks, of ISDN30 (i.e. up to 120 phone lines). The ISDN30E connections are identified by RJ45 connections. NTEs supporting older DASS-type protocols have co-axial connections. MPLS - Multi Protocol Label Switching A scalable private network, enabling multiple locations to connect to each other and transfer voice and data services via a private “cloud” arrangement. Associated with corporate organisations. SIP Session Initiation Protocol (SIP) is a signalling protocol, designed to initiate and terminate communications between multimedia communication sessions, mainly voice and video calls over the Internet or data networks. SIP Trunk A trunk is a way to get external calls in and out of the PBX. All extensions and accounts are internal, at some point someone will want to talk to other telephone users outside the PBX. This is done by using a trunk from the PBX to the telephone network. RTP The Real Time Transport Protocol (RTP) is an Internet protocol standard that specifies a way for programs to manage the real-time transmission of multimedia data over network services. In other words the voice part of Voice over IP. NAT Network Address translation (NAT) is the translation of an Internet Protocol address (IP address) between networks. One network is designated the inside network and the other is the outside. Typically, a company maps its local inside network address to a global outside (public) IP addresses. NAT unmaps the global IP addresses on incoming packets back into local IP addresses. This helps ensure security. It can also cause severe headaches without a NAT filter or session border controller CODEC Codec is designed to convert a signals - analogue to digital so that a data network can process the information. •GSM - 13 Kbps, 20ms •iLBC - 15Kbps - 20ms & 13.3 Kbps - 30ms •G.711 - 64 Kbps, (alaw/ulaw) •G.722 - 48/56/64 Kbps •G.723.1 - 5.3/6.3 Kbps, 30ms frame size •G.726 - 16/24/32/40 Kbps •G.728 - 16 Kbps •G.729 - 8 Kbps, 10ms •Speex - 2.15 to 44.2 Kbps •LPC10 - 2.5 Kbps •DoD CELP - 4.8 Kbps TCP – Transmission Control Protocol TCP (Transmission Control Protocol) is a set of rules (protocol) used along with the Internet Protocol (IP) to send data