In data processing systems, the time interval required to locate a particular data element, record, or file in a storage device.

Acronym for système electronique couleur avec memoire. A television signal standard (625 lines, 50 Hz, 220 V primary power) used in France, eastern European countries, the former USSR, and some African countries.

In the International System of Units (SI), the time interval equal to 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.

1. Dialtone presented to the call originator after an access code has been dialed for access to a second, outside, telecommunications system or service.
2. Dialtone returned to the call originator after she/he has dialed an access number and has reached a switch providing access to modem, to a fax machine, to another telephone, etc.

Of silica-based optical fibers, the transmission window at approximately
1. 3 m.
Note: The second window is the minimum-dispersion window in silica-based glasses. [After FAA]

In a system in which two channels share a common interface, a channel that has a lower data signaling rate (DSR) capacity than the primary channel.

Particles or radiation, such as photons, Compton recoil electrons, delta rays, secondary cosmic rays, and secondary electrons, that are produced by the action of primary radiation on matter.

A frequency standard that does not have inherent accuracy, and therefore must be calibrated against a primary frequency standard.
Note: Secondary standards include crystal oscillators and rubidium standards. A crystal oscillator depends for its frequency on its physical dimensions, which vary with fabrication and environmental conditions. A rubidium standard is a secondary standard even though it uses atomic transitions, because… (Read More →)

A radiodetermination system based on the comparison of reference signals with radio signals retransmitted from the position to be determined. [NTIA] [RR]
Note: An example of secondary radar is the transponder-based surveillance of aircraft. Synonym secondary surveillance radar.

See secondary emission.