B C D
E F G
H I J
K L M
N O P
Q R S
T U V
Radio frequency (RF).
A term used to describe incoming radio signals to a receiver or
outgoing signals from a radio transmitter
(above 150 Hz). Even though they are
radio signals, TV signals are included
in this category.
RAM. Random access
memory. Electronic chips, usually known as memory, holding digital
information while there is power
applied to it. Its capacity is measured in
kilobytes. This is
the computer's work area.
RAID. Redundant array
of inexpensive disks. This a technology of connecting a number of
hard drives into one mass storage
device, which can be used, among other
things, for digital
recording of video images.
In a camera that has a free-running horizontal sync as opposed to a 2:1
Refraction. The deflection
away from or towards the normal, of a beam of light as it passes
between two media of differing
Registration. An adjustment
associated with colour sets and projection TV's to ensure that the
electron beams of the three primary
colours of the phosphor screen are hitting
the proper colour
Resolution. A measure
of the ability of a camera or television system to reproduce detail.
The number of picture elements
that can be reproduced with good definition.
Usually measured in
Retrace. Also known
as flyback. The return of the electron beam in a CRT to the
point after scanning.
During retrace, the beam is typically
turned off. The Sync pulses are
generated during this time.
Remote control. A
transmitting and receiving of signals for controlling remote devices
pan and tilt units, lens functions,
wash and wipe control and similar. It may also refer to the
hand held controls for some VCRs
and other CCTV equipment.
Former name of the EIA association. Some older video test charts
carry the name
Radio frequency signal that belongs to the region up to 300 GHz.
A video coaxial cable with 75 Ohm characteristic impedance with larger
conductors than the
popular RG-59. With RG-11 much
longer distances can
than with RG-59, but it is more
expensive and harder to work
A coaxial cable designed with 50 Ohm characteristic impedance;
suitable for CCTV.
A video coaxial cable with 75 Ohm characteristic impedance. A
cable that is most common in use
in small to medium-size CCTV systems.
It has an outer
diameter of approx. 6 mm and it
is a good compromise between maximum distances
to 266m) and good transmission.
Rise time. The time
taken for a signal to make a transition from one state to another;
measured between the 10% and 90%
completion points of the transition.
Shorter or faster
rise times require more bandwidth
in a transmission channel.
RMS. Root Mean Square.
A measure of effective (as opposed to peak) voltage of an AC
waveform. For a sine wave
it is 0.7071 times the peak voltage. For any periodic
it is the square root of the average
of the squares of the values through one
cycle. For a
fixed resistive load, the RMS voltage
will give an equivalent heating effect to the DC voltage
of the same value as the RMS voltage.
ROM. Read Only Memory.
An electronic chip, containing digital information that does not
disappear when power is turned
An electronic device that routes a user-supplied signal (audio, video,
from any input to any user-selected
output. This is a broadcast term for
matrix switchers, as
we know them in CCTV.
RS. Recognised Standard.
A set of specifications for data transmission written by the
Electronics Industries Association
A SMPTE parallel component digital video standard.
A document prepared by the Electronics Industries Association describing
recommended practices for NTSC
colour television signals in the United States.
RS-232. A format of
digital communication using a three wire unbalanced presentation.
The RS-232 standard defines the
presentation and voltages for asynchronous communications,
but it does not define how the
data should be represented by the bits, i.e., it does not define
the overall message format and
protocol. It is very often used in computers, CCTV and
communications between keyboards
and matrix switchers.
RS-422. This is an
advanced format of digital communication when compared to RS-232.
A major difference is that the
presentation is balanced line and the signalling is differential.
In simple terms, the signal transmitted
is read at the receiving end as the difference between
wires without a reference to earth. So if there is common mode
the line, it will be cancelled
out. RS-422 can drive lines of up to 1200m and distribute
on to up to 10 receivers.
RS-485. This is an
advanced format of digital communications compared to RS-232. It
balanced line transmission system.
The major improvement
over RS422 is in the number of
receivers that can be driven with
this format, up to 32. It is classically a half duplex 2 wire