G.703
G.703, a standard based on Pulse-code modulation (PCM) standard, specifies voice over digital networks. Voice to digital conversion according to PCM requires a bandwidth of 64 kbps (+/- 100 ppm), resulting in the basic unit for G.703. G.703 specifies the physical and electrical characteristics of hierarchical digital interfaces at a rate up to 140Mbit/s.

G.704
G.704 defines the synchronous frame structure used at primary and secondary hierarchy levels on G.703 interfaces up to 45Mbit/s. The conventional use of G.704 on a 2Mbit/s primary rate circuit provides 30 discrete 64kbit/s channels, with a further 64kbit/s channel available for common channel signalling.

G.707
G.707 defines the Synchronous Digital Hierarchy (SDH) Bit Rates.

G.708
G.708 defines the Network Node Interface (NNI) for Synchronous Digital Hierarchy (SDH).

G.709
G.709 defines the Synchronous Multiplexing Structure.

G.711
G.711 is an ITU-T standard for audio companding released in 1972. It is primarily used in telephony. G.711 represents 8-bit compressed pulse code modulation (PCM) samples for signals of voice frequencies, sampled at the rate of 8000 samples/second. G.711 encoder will create a 64 kbit/s bitstream. There are two main algorithms defined in the standard: mu-law algorithm (used in North America & Japan) and a-law algorithm (used in Europe and other countries).

G.721
G.721 is a 32 kbps Adaptive Differential Pulse Code Modulation (ADPCM) speech compression algorithm. The sampling rate is 8 KHz. G.721 produces toll quality speech. With transmission error rates higher than 10.4, the perceived quality of G.721 is better than G.711. G.721 is the first ADPCM standard. Later came the standards of G.726 and G.727 for 40, 32, 24 and 16 kbps.

G.722
G.722 is a wideband speech coding algorithm supporting bit rates of 64, 56 and 48 kbps. In G.722, the speech signal is sampled at 16000 samples/second. G.722 can handle speech and audio signal bandwidth upto 7 kHz, compared with 3.6 kHz in narrow band speech coders. G.722 coder is based on the principle of Sub Band - Adaptive Differential Pulse Code Modulation (SB-ADPCM). The signal is split into two sub-bands and samples from both bands are coded using ADPCM techniques.

G.722.1
G.722.1 is an ITU-T standard for speech codecs that compresses 50Hz -7KHz audio signals into one of two bit rates, 24 or 32 Kbps.

G.723 or G.723.1
G.723, also known as G.723.1 in more precise terms, is a standard-based voice codec providing voice quality (300 Hz to 3400 Hz) at 5.3 / 6.3 kbps. It was designed for video conferencing/telephony over standard phone lines, and is optimized for real-time encoding & decoding. G.723.1 is part of the H.323 (IP) and H.324 (POTS) standards for video conferencing.

G.726
G.726 is a ITU-T speech codec based on ADPCM operating at bit rates of 16-40 kbit/s. The most commonly used mode is 32 kbit/s, since this is half the rate of G.711, thus increasing the usable network capacity by 100%. G.726 specifies how a 64 kbps A-law or µ-law PCM signal can be converted to 40, 32, 24 or 16 kbps ADPCM channels where the 24 and 16 kbps channels are used for voice in Digital Circuit Multiplication Equiment (DCME) and the 40 kbps is for data modem signals (especially modems doing 4800 kbps or higher) in DCME.

G.727
G.727 is an embedded Adaptive Differential Pulse Code Modulation (ADPCM) algorithms at rates of 40, 32, 24 and 16 kbit/s. G.727 defines the transcoding law when the source signal is a pulse-code modulation signal at a pulse rate of 64 kbit/s developed from voice frequency analog signals as fully specified by G.711.

G.728
G.728, based on the Low-Delay Code Excited Linear Prediction (LD-CELP) compression principles, is a 16 kbps compression standard. G.728 has an algorithmic coding delay of 0.625 ms. G.728 normally compresses toll quality speech at 8000 samples/second. G.728 Annex G (G.728 G) is a fixed point specification of the coder working at a bit rate of 16000 bits/second. G.728 Annex I (G.728 I) is the packet loss concealment (PLC) technique used along with G.728 G. G.728 coders are widely used for applications of telephony over packet networks, especially voice over cable and VoIP, where low delay is required.

G.729
G.729 is an audio data compression algorithm for voice that compresses voice audio in chunks of 10 milliseconds. G.729 does coding of speech at 8 kbit/s using Conjugate-Structure Algebraic-Code-Excited Linear-Prediction(CS-ACELP). G.729 is mostly used in Voice over IP (VoIP) applications for its low bandwidth requirement. Standard G.729 operates at 8 kbit/s, but there are extensions, which provide also 6.4 kbit/s and 11.8 kbit/s rates for marginally worse and better speech quality respectively. Also very common is G.729a which is compatible with G.729, but requires less computation.

G.729 A/B
G.729 A/B is an ITU-T standard for speech codecs that provides near-toll quality audio at 8 Kbps. G.729 Annex A is a reduced complexity codec and G.729 Annex B supports silence suppression and comfort noise generation.

G.780
G.780 defines the terms for SDH Networks and Equipment.

G.781
G.781 defines the structure of Recommendations on Equipment for the Synchronous Digital Hierarchy (SDH).

G.782
G.782 defines types and characteristics of Synchronous Digital Hierarchy (SDH) Equipment

G.783
G.783 defines characteristics of Synchronous Digital Hierarchy (SDH) Equipment Functional Blocks.

G.7xx
G.7xx is a suite of ITU-T standards for audio compressions and de-commpressions. It is primarily used in telephony. In telephony, there are 2 main algorithms defined in the standard, mu-law algorithm (used in America) and a-law algorithm (used in Europe and the rest of the world). Both are logarithmic, but the later a-law was specifically designed to be simpler for a computer to process. G.7xx codec suite includes G.712, G.721, G.722, G.723, G.726, G.727, G.728, G.729 etc.

G.803
G.803: Architecture of Transport Networks Based on the Synchronous Digital Hierarchy (SDH)

G.804
G.804 is the ITU-T framing standard that defines the mapping of ATM cells into the physical medium.

G.832
G.832: Transport of SDH Elements on PDH Networks: Frame and Multiplexing Structures

G.DMT
G.DMT, another name for ITU G.992.1, is an ITU standard for ADSL using discrete multitone modulation.

G.Lite
G.Lite, also known as ADSL Lite and Splitterless ADSL, is one of the Digital Subscriber Line technologies that allows broadband data access over normal phone lines (twisted pair cables, also called POTS). G.Lite offers a maximum of 1.5 Mbit/s downstream and 512 kbit/s upstream and does not require the use of phone line splitters.

Gateway Redundancy
Gateway Redundancy refers to a feature that enables the Gatekeeper to request that other Gatekeepers search their zones to locate a Gateway when Line Hunting fails to find a suitable service provider. If there is no service provider available, the Gateway Redundancy policy reables the Gatekeeper to complete the call by referring the call to other Gatekeepers.

Gateway Supported Prefixes
Gateway Supported Prefixes refers to some features in standard of H.323 version 2. It enables a Gateway to specify prefixes that the user should dial before the WAN number in order to make a call using a certain medium.

Gateway Switched Exchange
Gateway switched exchange is the exchange that on top of trunk exchanges for international calls. The international gateway switch provides connections between different countries that have a wide range of operating parameters. Specifically, a gateway switch must support conversions between different signaling formats. Another issue for international calls is voice quality and echo control.

GETS: Government Emergency Telecommunications Service
Government Emergency Telecommunications Service (GETS) is a White House-directed emergency phone service provided by a division of the Department of Homeland Security. GETS uses enhancements based on existing commercial telecom technologies.

GIS: Geographical Information System
Geographical Information System (GIS) refers to a computer system capable of capturing, storing, analyzing, and displaying geographically referenced information, that is, data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel, and spatial data that go into the system.

Globalstar
Globalstar is a low earth orbit satellite system that deploys a network of 48 satellites to create a global voice and data service. This system is backed by Qualcomm, Loral, and Alcatel.

GloBanD
GloBanD is an European Switched Nx64 data service consisting of a single circuit whose bandwidth is a multiple of 64 kbps. This circuit consists of one or more B channels. For example, if a caller requests 512 kbps service, the line uses 8 B channels to supply the requested bandwidth. This service is available over T1 PRI lines only, and follows the CCITT Q.931 recommendation. It differs from MultiRate in being an overlay network, rather than an integral part of the worldwide switched digital infrastructure.

GNE: Gateway Network Element
Gateway Network Element (GNE) refers to a Network Element (NE) that provides connections to other Network Element in most telecommunication and network systems, such as SONET/SDH/DLC, etc. GNE has a list of nests connected to it and their TIDs in the form of a route table. Whenever an input message comes to the GNE, it will route it to the appropriate NE using the TID in the route table.

GOS: Grade Of Service
Grade of Service (GOS) is a measure of the success a subscriber is expected to have in accessing a network to complete a call. The grade of service is usually expressed as percentage of calls attempted by the subscriber during the busy-hour that are blocked due to insufficient network resources. The other measures for service quality is called Quality of Service (QoS) for the quality of voice service.

GOSIP: Government Open System Interconnection Profile
Government Open System Interconnection Profile (GOSIP) is a subset of OSI standards specific to US Government procurements, designed to maximize interoperability in areas where plain OSI standards are ambiguous or allow options.

GPON: Gigabit PON
Gigabit PON (GPON) is a Passive Optic Network (PON) technology operating at bitrates of above 1 Gb/s. Apart from the need to support higher bitrates, the overall protocol has been opened for re-consideration and the sought solution should be the most optimal and efficient in terms of support for multiple services, OAM&P functionality and scalability.

Ground Start
Ground Start is a method of signaling used primarily on Central Office (CO) trunk lines to PBXs. A ground is placed on one side of the two-wire line to indicate that it is in use so the other side of the two-wire interface does not attempt to use the line.

Ground Start Signaling
Ground-start signaling is a type of analog voice grade access line signaling in the telephone system that requires the customer interface to provide a ground on the ring conductor at the network interface to initiate service requests.

Ground-Start Trunk
Ground-start Trunk is a phone line that uses a ground instead of a short (loop-start trunks use a short between tip and ring) to signal the central office for a dial tone.

Group 3
Group 3 is an ITU-T standard relating to fax devices. A Group 3 fax device is a digital machine containing a 14400 baud modem that can transmit an 8 1/2 by 11 inch page in approximately 20 seconds with a resolution of either 203 by 98 dots per inch (dpi) or 203 by 196 dpi (fine), using Huffman code to compress fax data. Group 3 faxes use a standard dial-up telephone line for transmission.

Group Busy Tone
Group Busy Tone is audible tone of telephone system that is indicated by low tone on the sleeve of trunk jacks at cord switchboards. Absence of the tone tells the operator that there is at least one idle trunk in a group. Group Busy Tone is a steady Low Tone.

GTT: Global Title Translation
Global Title Translation (GTT) is a function usually performed in a Signal Transfer Point (STP). GTT is the procedure by which the destination signaling point and the subsystem number (SSN) is determined from digits (that is, the global title) present in the signaling message.