| dc Power Block: |
A device which stops the flow of dc power but permits passage of higher frequency ac signals. |
| De-Emphasis: |
The restoration of a pre-emphasized signal wave to its original form (see Pre-Emphasis). |
| Decibel (dB): |
A logarithmic function used to simplify CTN calculations. Decibels may be added or subtracted. 0 dB is the standard reference level for all CTN calculations. The logarithimic ratio of power levels used to indicate gains or losses of signals. Decibels relative to one watt, milliwatt and millivolt are abbreviated as dBm V is used as the standard reference for all SMATV calculations. |
| Decoder: |
A circuit that restores a signal to its original form after it has been scrambled. |
| Demodulator: |
A device which detects ths signal from the carrier, usually the I.F. frequency. It eliminates the carrier from signal, retaining the intelligence portion (video, audio or data) for further processing. A device which extracts the baseband signal from the transmitted carrier wave. |
| Detent Tuning: |
Tuning into a channel by selecting a preset resistance. |
| Dielectric: |
An electrical insulator in which the electrical field can by sustained with a minimum dissipation of its energy. |
| Digital: |
Describes a system or device in which information is transferred by electrical "on-off", "high- low", or "1/0" pulses instead of continuously varying signals or states as in an analog message. |
| Digital-to-Analog Converter: |
A circuit that converts digital signals into their equivalent analog form. |
| Diplexer: |
A device that combines RF frequencies (not power assigned) and satellite frequencies (power assigned) on to one coax. Diplexers can also separate satellite and RF signals. |
| Discrete Stereo: |
A method of transmitting stereo in which the left and right channels are contained on completely separate subcarriers. To tune in this type of stereo, two completely separate subcarrier tuners are needed. The demodulator side of the deviation from a standard center frequency, the tuning frequency of the F.M. signal. |
| Distribution System: |
A system consisting of coax that carries signals from the headend to each video location. |
| Drifting: |
An instability in a preset voltage, frequency or other electronic circuit parameter. |
| Drop Cable: |
The cable used to route a signal from outside distribution equipment to a television. |
| Echo: |
A signal which has been reflected at one or more points during transmission with sufficient magnitude and time difference as to by detected as a signal distinct from that of the primary signal. Echoes can be either leading or lagging the primary signal and appear as reflection, or "ghosts" in an AM system. |
| Egress Interference: |
An undesired leakage of radiation from a cable or other closed circuit system. |
| Encoder: |
A device for scrambling a signal. |
| F-Connector: |
A standard RF connector used to link coax cables with electronic devices. |
| FCC: |
The Federal Communications Commission, the regulatory board which sets standards for communication within the United States. |
| Feeder Line: |
The coaxial cable serving as a subtrunk to feed drop cables. |
