Functional Block Diagram - Blonder Tongue Laboratories Inc.

Broadband Specification Guide
CATV Terms & Definitions
Core
The light conducting portion of an optical waveguide. It is composed of
a high refractive index material made typically of silicon tetrachloride
(SiC14). The addition of germanium tetrachloride (GeC14) increases the
refractive index of the core and creates an index gradient along a waveguide.
Core Diameter
The diameter of the circle that circumscribes the core area.
Cross Modulation
Interference created by operating equipment beyond limitations. In TV
broadband RF amplifiers it produces a “windshield wiper” interference on
the screen. In severe cases video content from another channel can be seen.
Couplers
In fiber optics, a device which links three or more fibers, providing two or
more paths for the transmission signal. In an "active" coupler, a switching
mechanism selects among several routes; in a "passive" coupler, routing
is determined by the geometry of the device.
Cross-modulation (X-Mod)
Modulation (intelligence or information) that is superimposed onto a
different modulated or un-modulated carrier, from another modulated
carrier that is present, when both signals are passed through a nonlinear circuit.
Cycle
One complete sequence of values of an alternating wave starting at zero,
increasing to a maximum positive value, decreasing to zero, increasing
to a maximum negative value, and decreasing to zero again. Also called
a Hertz.
DBS
Direct Broadcast Satellite. Pending high power Ku-Band satellite service
to provide programming directly to home subscribers via small diameter
(3 feet or less) parabolic antennas.
Decibel (dB)
1. A logarithmic unit of measure expressing the ratio of two discrete
levels, input and output for example, of power, voltage, or current.
May be used to denote either loss (-dB) or gain (+dB). One cannot
denote input or output signal level in dB, but one can denote gain or
loss in dB.
2. The standard unit used to express gain or loss of power.
Decibel-millivolts (dBmV)
A logarithmic unit of measure of absolute power, voltage, or current. The
dB denotes a ratio between two levels (see Decibel) but the qualifying
term mV establishes one of the levels as a reference. Zero dBmV (0
dBmV) is one millivolt (0.001 or 10-1 volts) measured across a 75 Ω
impedance. Since the impedance is specified and fixed (75 ohms), 0
dBmV is also a reference power level of 0.0133 microwatts. One cannot
denote cable loss or amplifier gain in dBmV, but one can denote input or
output signal levels in dBmV.
Decibel-milliwatt (dBm)
A unit of power. Decibels referenced to a unit of one milliwatt.
Zero dBm = I mW.
Decibel-Watt (dBW)
A unit of power. Decibels referred to a unit of one watt. Zero dBW = I Watt.
Demodulator
Device that provides baseband audio and video outputs from a TV
channel input.
Detect
To rectify a modulated carrier wave and thereby recover the original
modulating wave.
Detection
The process by which a wave corresponding to the modulating wave is
obtained from a modulated wave.
Dielectric
A nonconducting (insulating) material, such as glass.
Digital Signal
A signal which is expressed by discrete states. For example, the absence
or presence of a voltage, the level of amplitude of a voltage, the duration
of the presence of a voltage, etc. Information or intelligence to be
transported may be assigned value or meaning by combinations of the
discrete states of the signal using a code of pulses or digits.
Directional Coupler
A network or device that diverts a predetermined amount of its input
signal to one of two outputs, with the remaining balance of the input
energy being presented to a second Output.
Dichroic Filter
An optical filter designed to transmit light selectively according to
wavelength (most often, a high-pass or low-pass filter.
Dichroic Mirror
A mirror designed to reflect light selectively according to wavelength.
Diffraction
The deviation of light rays from the paths predicted by geometrical optics.
Diffraction Grating
An array of fine, parallel, equally spaced reflecting or transmitting lines
that mutually enhance the effects of diffraction to concentrate the
diffracted light in a few directions determined by the spacing of the lines
and the wavelength of the light.
Digital
Referring to the use of digits to formulate and solve problems, or to
encode information.
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