T-1DM T1 digital multiplexing. The multiplexing of 23 channels of 64 kbps each into a single 1.544 Mbps signal, and using the 24th channel to carry header information.

T-1. A T-carrier composed of 23 voice channels which can each carry 64 kbps. The 24 channels are aggregated to form a single channel having the capacity to carry 1.5 Mbps. The T-1 system is the standard for the regular local telephone service.

T-2. A T-carrier with four times the capacity of the T-1 carrier. T-2 has a can carry 6.312 Mbps (equivalent to 96 voice conversations).

T-3. A T-carrier with 28 times the capacity of the T-1 carrier. The T-3 carrier can carry 44.736 Mbps (equivalent to 672 voice conversations).

T-4. A T-Carrier with 168 times the capacity of the T-1 carrier. The T-4 carrier can carry 274.176 Mbps (equivalent to 4032 voice conversations).

TACS (Total Access Communications System). An analogue standard for mobile systems.

Tariff. A document that outlines the agreement between regulating agencies and service providers for rates for services or goods within a given area.

T-carrier. The AT&T hierarchy of digital systems that carry signals in digital format. The T-carriers are designated T-1, T-2 and T-4.

TCH (Traffic Channel). The TCH carries the user's telephone conversations. In the case of a digital cellular network, it carries digitized samples of the telephone conversations.

TCP (Transmission Control Protocol). A method for sending data [packets] over the Internet. It works with IP and divides the data into packets, keeps track of them as they traverse the most efficient route through the Internet and reassemble them at the far end. It is connection-oriented, in that the connection is maintained for the delivery duration.

TDM (Time Division Multiplexing). A system that interleaves data from several sources onto a single serial bit stream.

TDMA (Time Division Multiple Access). A technology used in digital cellular telephone communication to divide each cellular channel into a number of time slots in order to increase the amount of data that can be carried. This technology is called multiplexing. TDMA is used by Digital-American Mobile Phone Service (D-AMPS), Global System for Mobile communications (GSM), and Personal Digital Cellular (PDC). TDMA is implemented within each of these systems differently. An alternative multiplexing scheme to TDMA is code division multiple access (CDMA), which takes the entire allocated frequency range for a given service and multiplexes information for all users across the spectrum range at the same time. The TDMA standard was first specified in Interim Standard 54 (IS-54). The U.S. uses IS-136 for TDMA for both the cellular (850 MHz) and PCS (1900 MHz) spectrums. TDMA is also used for Digital Enhanced Cordless Telecommunications (DECT).

TDD: Time Division Duplex. In a TDD system simultaneous transmission and reception of radio signal is possible. This allows the mobile phone user to talk and listen at the same time. The mode of communication is facilitated by having different time slots within a TDMA scheme whereby transmission and reception take place a different times so as to avoid interfering with one other

TD-SCDMA: Time Division Synchronous CDMA. TD-SCDMA is a variant of CDMA. It is the basis of the Chinese proposal for IMT-2000 standardization.

TDT (Time and Data Table). An optional DVB SI table that updates the IRD's clock.

Telecommunications. The transmission of voice or data using telephones or any other media.

Telecommuting. Working outside the traditional workplace, usually at home using telecommunications to deliver completed work tasks to the employer. Factors affecting telecommuting include the availability of sufficient bandwidth and telecommunications infrastructure in a given area.

Teleservice. A teleservice provides subscribers with the ability to communicate with other subscribers. Teleservices include basic telecommunications services, for example, voice telephony, voice mail, and GSM specific services.

Terminal. A connecting point for equipment, power, or a signal, such as a mobile station or a computer terminal.

TIA (Telecommunications Industry Association). The TIA was formed in 1988 as a result of the merger of the US Telephone Suppliers Association and the information technology group of the EIA. The TIA and EIA collaborate closely in producing standards that must be approved by ANSI before becoming US standards.

TLS (Transport Layer Security). TLS is a protocol that provides data integrity and privacy on a communications link over the Internet. It allows client-server applications to communicate and is designed to prevent eavesdropping, message forgery and interference.

TMSI (Temporary Mobile Station Identity). TMSI is used for signaling between the MS and the MSC. TMSI is used instead of the IMSI for security reasons.

Toll ticket. The lowest level of call data description. Created by the MSC when a subscriber roams from one cell to another and a handover is initiated. Subscribers pay extra for the privilege of cell roaming. A new toll ticket is generated for each handover. The toll tickets are collated at the end of the call and the subscriber is billed accordingly.

Trailer. Protocol control information located at the end of a PDU.

Transceiver. A device consisting of a transmitter and a receiver that transmits and receives signals.

Transform Coding. See Intra-frame Coding.

Transponder. A satellite component that receives, modulates, amplifies and retransmits a signal. It consists of all the components that identify one Channel.

TS (Traffic Shaping). A mechanism that alters the traffic characteristics of a stream of cells on a connection to achieve better network efficiency, while meeting the quality of service (QoS) objectives, or to ensure conformance at a subsequent interface. Traffic shaping must maintain cell sequence integrity on a connection. Shaping modifies traffic characteristics of a cell flow with the consequence of increasing the mean Cell Transfer Delay.

TS (Transport Stream) . The DVB /MPEG-2 data stream that transmits several digital TV programs, with different time bases, in one Channel. It contains fixed-length packets, each of 188 bytes.

TSS (Telecommunication Standards Sector). An international organization that defines standards for telecommunication devices.

TTC: Telecommunications Technology Committee. TTC is a Japanese telecommunications standards body.