Online Computer Terms Dictionary - C

Carrierless Amplitude/Phase Modulation

<communications> (CAP) A design of Asymmetric Digital Subscriber Line transceiver developed by Bell Labs. CAP was the first ADSL design to be commercially deployed and, as of August 1996, was installed on more lines than any other.

CAP is a variation of Quadrature Amplitude Modulation, the modulation used by most existing modems in 1997. With CAP, the three channels (POTS, downstream data and upstream data) are supported by splitting the frequency spectrum. Voice occupies the standard 0-4 Khz frequency band, followed by the upstream channel and the high-speed downstream channel.

(1997-10-08)

carrier scanner

<security> (Or "wardialer") A program which uses a modem to dial a series of phone numbers (say, from 770-0000 to 770-9999), and keeps a log of what phone numbers answer with a modem carrier. The results of such a search were generally used by people looking to engage in random mischief in random machines.

Since the 1980s, wardialers have generally fallen into disuse, partly because of easily available "caller ID" technology, partly because fax machines are now in wide use and would often be logged as a carrier by a wardialer, and partly because there are so many new and more interesting venues for computerised mischief these days.

(1997-03-16)

carrier signal

<communications> A continuous signal of a single frequency capable of being modulated by a second, data-carrying signal. In radio communication, the two common kinds of modulation are amplitude modulation and frequency modulation.

(1995-03-01)