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- Ampere (or amp): measurement of electrical current.
- Alternating current: type of electrical current.
- See Dolby AC-3.
- The general term for the ability of a telecommunications user to make use
of a network.
- Analogue-to-digital conversion: process of converting analogue signals to
a digital representation. DAC represents the reverse translation.
- Ad hoc capacity
- Capacity available for bookings on a temporary basis; see Occasional capacity.
- Adaptive differential pulse code modulation.
- Refers to the computational code used to compress or decompress a signal.
- Amplitude modulation.
- Device used to increase the power of an electronic signal.
- Amplitude modulation
- Process where a baseband message signal modulates (alters) the amplitude and
frequency of a high-frequency carrier signal, which is at a nominally fixed frequency,
so that the carrier signal varies in amplitude.
- Signal which can take on a continuous range of values between a minimum and
a maximum value; method of transmitting information by continuously variable quantities,
as opposed to digital transmission, which is characterized by discrete 'bits'
of information in numerical steps.
- Canadian domestic satellite system.
- American National Standards Institute (US).
- Device for transmitting and receiving radio waves; in SNG, the directional
parabolic antenna used for satellite transmissions.
- Atlantic Ocean Region: describes coverage area of a satellite.
- Cross-sectional area of a parabolic antenna.
- The point in a satellite's orbit when it is furthest away from the Earth.
- Imperfections in a digital signal caused by the compression process.
- Asynchronous serial interface: DVB compliant signal.
- Asynchronous transfer mode: division of digital signals into small packets
and transmitted in small, fixed-size data 'cells'.
- Atmospheric losses
- Losses caused by the travel of the signal through the atmosphere - encountered
on both the uplink and the downlink.
- Loss in power of electromagnetic signals between transmission and reception
- Attitude control
- Orientation of the satellite in relationship to the Earth and the Sun.
- Audio sub-carrier
- An extra carrier typically between 5 and 8 MHz carrying audio information
on top of a video carrier.
- Automatic frequency control
- AFC: circuit which automatically controls the frequency of a signal.
- Automatic gain control
- AGC: circuit which automatically controls the gain of an amplifier so that
the output signal level is virtually constant for varying input signal levels.
- The percentage of time over a year that a satellite link will be received
successfully. Not particularly applicable to SNG uplinks.
- Angle of rotation (horizontal) that a parabolic antenna must be rotated through
to point to a specific satellite in a geosynchronous orbit; the compass bearing
of the satellite in the horizontal plane from a point on the Earth's surface.