(adj.)Refers to the transmission of data in just one direction at a time. For example, a walkie-talkie is a half-duplex device because only one party can talk at a time. In contrast, a telephone is a full-duplex device because both parties can talk simultaneously. Duplex modes often are used in reference to network data transmissions.
Some modems contain a switch that lets you select between half-duplex and full-duplex modes. The correct choice depends on which program you are using to transmit data through the modem. In half-duplex mode, each character transmitted is immediately displayed on your screen. (For this reason, it is sometimes called local echo — characters are echoed by the local device). In full-duplex mode, transmitted data is not displayed on your monitor until it has been received and returned (remotely echoed) by the other device. If you are running a communications program and every character appears twice, it probably means that your modem is in half-duplex mode when it should be in full-duplex mode, and every character is being both locally and remotely echoed.
- half height
Some older PCs supported both full-height and half-height bays for disk drives and other mass storage devices. Today, all bays are half-height.
- half life
Also called life expectancy or shelf life, the time it takes for a data-storing medium to lose half of its strength. Floppy disks and magnetic hard drives have a half life of between five and seven years. Optical media, such as CD-Rs, have a half life of about 30 years. The term comes from the […]
In printing, a continuous tone image, such as a photograph, that has been converted into a black-and-white image. Halftones are created through a process called dithering, in which the density and pattern of black and white dots are varied to simulate different shades of gray. In conventional printing, halftones are created by photographing an image […]
(1) A person who is licensed to operate a ham radio. (2) Automatic spam filters classify e-mail as either spam or ham (meaning not spam).
- ham radio
Amateur radio communication in a range of frequencies from just above the AM broadcast band (1.6 MHz) to the microwave region, at several hundred gigahertz. These frequencies have been designated for amateur use by the FCC. Anyone with a radio receiver or a radio scanner can listen in on ham radio communications, but only an […]