AT Command – This is the character “@” and usually means “at”.
AT&T – American Telegraph and Telephone, the inventors of the first modem.
Attended Mode – This is the mode in which two or more users manually enter commands to send or receive files.
Attenuation – The phenomenon that is the loss in the power of electromagnetic signals between their transmission and receiving points.
Audio Monitor – This is a speaker that is part of the modem and allows you to hear sound on the phone line.
Auto Answer – This is when a modem, phone, or other device has the capability to automatically set up a connection with an incoming transmission.
Auto Baud – The ability of a modem to adapt its communication rate if the computer it is communicating with is unable to connect at the requested speed.
Auto Dial – When a phone or other device allows the dialing a one or a few numbers to cause the dialing of a long string of numbers.
Auto Redial – When a phone or modem redials a number if it encounters a busy signal the first time around.
Auto Reply – To send a message immediately upon the reception of one.
Automatic Frequency Control (AFC) – A circuit that can automatically control a signal’s frequency.
Automatic Gain Control (AGC) – A circuit that automatically governs the gain of an amplifier so that the output signal level remains essentially constant (even if there are varying input signal levels).
AZ/EL Mount – This is an adjustable antenna mount.
Azimuth – Generally, this is the angular distance along the horizon to the location of the object (measured in degrees). By convention, azimuth is measured from north, rotating towards the east, along the horizon. Regarding satellites specifically, it is the horizontal angle of rotation that a parabolic antenna located on the ground must be rotated through to point towards a specific satellite in space.