Synonym (in telephony) main distribution frame.

Of an antenna radiation pattern, the lobe containing the maximum power (exhibiting the greatest field strength).
Note: The horizontal radiation pattern, i.e., that which is plotted as a function of azimuth about the antenna, is usually specified. The width of the main lobe is usually specified as the angle encompassed between the points where the power has fallen 3 dB… (Read More →)

A user instrument, e.g., telephone set or terminal, with a distinct call number designation, connected to a local loop, used for originating calls, and on which incoming calls from the exchange are answered.

In a computer, program-addressable storage from which instructions and other data may be loaded directly into registers for subsequent execution or processing.
Note 1: Main storage includes the total program-addressable execution space that may include one or more storage devices.
Note 2: "Main storage" usually refers to large and intermediate computers, whereas "memory" usually refers to microcomputers, minicomputers, and calculators.

A large computer, usually one to which other computers and/or terminals are connected to share its resources and computing power.

1. A characteristic of design and installation, expressed as the probability that an item will be retained in or restored to a specified condition within a given period of time, when the maintenance is performed in accordance with prescribed procedures and resources.
2. The ease with which maintenance of a functional unit can be performed in accordance with prescribed requirements.

1. Any activity, such as tests, measurements, replacements, adjustments and repairs, intended to restore or retain a functional unit in a specified state in which the unit can perform its required functions.
2. [For materiel], All action taken to retain materiel in a serviceable condition or to restore it to serviceability. It includes inspection, testing, servicing, classification as to serviceability,… (Read More →)

In a communications link, a circuit used by maintenance personnel for coordination.
Note: An MCC is not available to operations or technical control personnel.

1. A trapdoor in software that allows easy maintenance and development of additional features and that may allow entry into the program at unusual points or without the usual checks. [2382-pt.8]
2. Special instructions (trapdoors) in software allowing easy maintenance and additional feature development. Since maintenance hooks frequently allow entry into the code without the usual checks, they are a… (Read More →)

Key intended only for in-shop use. [INFOSEC-99]