Glossaries

• Add Drop Multiplexer (ADM)
• Equipment in a fiber optic network that combines multiple signals into one single signal for further transmission. The "add drop" means that it can add or extract single signals from the major transmission route similar to on/off-ramps in a highway.
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• Advanced Encryption Standard (AES)
• An algorithm for the encryption of electronic data. It has growingly replaced Data Encryption Standard (DES) nowadays. It adopts the symmetric-key algorithm, which indicates that the same key is used for both encrypting and decrypting the data.
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• Alarm Cut Off (ACO)
• Button or similar feature that allows all alarm signals to be manually silenced.
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• Alarm Indication Signal (AIS)
• In a T1 network, this is the signal is sent to let the receiver know that a fault has happened earlier in the transmission path. The signal is also called "all ones" because a transmission of all 1s is sent to maintain transmission continuity.
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• Alternate Mark Inversion (AMI)
• A type of line code used in E1 and T1 networks. With AMI, zeros are represented as 0 volts during each bit cell or clock cycle, while ones are represented as a positive voltage in one clock cycle and a negative voltage in the next one. This prevents a sufficient DC voltage from building up as well as maintaining "ones density" for clock recovery.
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• American National Standards Institute (ANSI)
• A private, non-profit, voluntary organization that coordinates standard relating activities, approves US national standards, and represents the United States in international standard organizations. It creates standards in computers, networking, telecommunications, and a variety of other engineering fields.
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• Automatic Ring Down (ARD)
• A setup where two telephones are connected such that lifting the handset of one will cause the other to ring immediately. This is used primarily by busy financial market traders and military units.
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• Available Second (AS)
• A measure of time during which service is available to the paying customer.
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• Asynchronous Transfer Mode (ATM)
• A standard switching technique that can be used to carry many different service types such as voice, video, or data all over one network. It does this by dividing the data stream into fixed length cells of size 53 bytes, which thus can be more easily implemented in hardware. ATM also goes by the connection-oriented model which establishes a "virtual circuit" connection between data points before it transmits data.
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• American Wire Gauge (AWG)
• A standardized system to measure the diameter of round, electrical carrying copper wire. The cross-sectional area of the wire is an important factor in determining the amount of current that it can carry. Numbers are integers that vary from 36 (very thin) to 0 (relatively thick).
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