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 T1 channels.  In North America, a digital transmission channel carrying data at a rate of
1.544 Mbps.  In Europe, a digital transmission channel carrying data at a rate of 2.048 Mbps.
TBC.  Time Base Correction.  Synchronization of various signals inside a device or
system, such as a multiplexer or a time base corrector.
TCP/IP  Transmission Contorl Protocol / Intenet Protocol
TDG.  Time and Date Generator.
TDM.  Time Division Multiplexing.  Time-sharing of a transmission channel by assigning
each user a dedicated segment of each transmission cycle.  Video Multiplexers in CCTV
use TDM techniques to record many signals onto a single tape.
Tearing.  A lateral displacement of the video lines due to sync instability.  It appears as though
parts of the images have been torn away.
Teleconferencing.  Electronically linked meeting conducted among groups in separate
geographic locations.
Telemetry.  Serial data used for the remote control (or monitoring) of a system.  Usually comprises a
digital encoded data, which is represented by voltages on the line.  Sometimes the signal
can be audio tones, such as Frequency Shift Keying (FSK) or Dual Tone Multi Frequency
(DTMF).  It is intended to control pan, tilt, zoom, focus, preset positions, wash, wipe and
similar.  Being digital, it is usually sent via twisted pair cable but it can also be transmitted
over the video coaxial cable, in the opposite direction to the video.
Telephoto.  A lens where the focal length is longer than the physical length of the lens,  not
to be confused with a zoom lens.
Termination.   1. The connection of a discreet impedance at the end of a transmission line.
When the characteristic impedance of the cable (75 Ohms in CCTV) is the value used (as
should always be the case) the maximum power is transferred with no reflections.
2.  It can refer to the physical act of terminating a cable with a special connector, which for
coaxial cable is usually BNC.  For optical fibre cable, the most common Termination in CCTV
is the ST connector.
TFT.  Thin-Film-Transistor.  This technology is used mainly for manufacturing flat computer
and video screens that are superior to the classic LCD screens.  Colour quality, fast response
time and resolution are excellent for video.
Time lapse VCR (TL VCR).  A video recorder, most often in VHS format, that can prolong
the video recording on a single tape up to 960 hours (this refers to a 180 min tape).  This
type of VCR is often used in CCTV systems.  The principle of operation is very simple -
instead of having the video tape travel at a constant speed of just under 24mm/s (which is
the case with the domestic models of VHS VCRs), it moves with discrete steps that can be
controlled.  TL VCRs can have a number of other special functions for use in CCTV systems.
Time lapse video recording.  The intermittent recording of video signals at intervals to extend
the recording time of the recording medium.  It is usually measured when using a 3-hr
(180-min) tape.
T-pulse to bar.  A term relating to frequency response of video equipment.  A video signal
containing equal amplitude T-pulse and bar portions is passed through the equipment and the
relative amplitudes of the T-pulse and bar are measured at the output. A loss of response is
indicated when any portion of the signal is lower in amplitude than the other.  The test signal
is called a Pulse and Bar signal and often includes a 2T a 10T a bar and a ramp signal, which
contains low medium and high frequencies.
Touchscreen.  A computer type screen that enables selection similar to a computer mouse but
operates by touching the screen.  The operation is usually either based on capacitance or
Surface Acoustic Waves (SAW).
Tracking.  The angle and speed at which the tape passes the video heads.
Transcoder.  A device that converts one form of encoded video to another, e.g., to convert
NTSC video to PAL.  Sometimes mistakenly used to mean translator.
Transducer.  A device that converts one form of energy into another.  For example, in fibre
optics, a device that converts light signals into electrical signals.
Translator.  A device used to convert one component set to another, e.g., to convert Y, R-Y,
B-Y signals to RGB signals.
Transponder.  The electronics of a satellite that receives an uplinked signal from the earth,
amplifies it, converts it to a different frequency and returns it to the earth.
TTL.  1.  Transistor-Transistor Logic.  A term used in digital electronics mainly to describe the
ability of a device or circuit to be connected directly to the input or output of digital
equipment.  Such compatibility eliminates the need for interfacing circuitry. TTL signals
are usually limited to binary i.e.. two states, low and high, and are thus much more limited
than analogue signals.  2.  Thru-The-Lens viewing, metering or colour measuring.
TVL.  TeleVision Lines.  The measure of resolution of either a camera output or a monitor
display.  It is limited by the frequency response of the system or the Chroma sub carrier.
Twisted-pair.  A cable composed of two small insulated conductors twisted together.  Since
both wires have nearly equal exposure to any interference, common mode noise is high, but
the differential noise is slight thus common mode noise is rejected in a twisted pair line.  Twisted
pair cable is used for balanced line transmission.
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