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The NEAR warning device. The National Emergency Alarm Repeater (NEAR) was a civilian emergency warning device in the United States. It was a 2–3" (5–7.5 cm) square box designed to plug into a standard power outlet to receive a special signal sent over the electric power transmission lines.
An amateur radio repeater system consisting of a 70 cm repeater and a 2-meter digipeater and iGate. Coaxial cavity RF filter at 2 meter repeater An amateur radio repeater is an electronic device that receives a weak or low-level amateur radio signal and retransmits it at a higher level or higher power, so that the signal can cover longer ...
A radio repeater is a combination of a radio receiver and a radio transmitter that receives a signal and retransmits it, so that two-way radio signals can cover longer distances. A repeater sited at a high elevation can allow two mobile stations, otherwise out of line-of-sight propagation range of each other, to communicate. [ 1 ]
The first relay system with radio repeaters, which really functioned, was that invented in 1899 by Emile Guarini-Foresio. [2] A radio repeater usually consists of a radio receiver connected to a radio transmitter. The received signal is amplified and retransmitted, often on another frequency, to provide coverage beyond the obstruction.
Receivers in a system using 67.0 Hz can take noticeably longer to decode than ones using 203.5 Hz, and they can take longer than one decoding 250.3 Hz. In some repeater systems, the time lag can be significant. The lower tone may cause one or two syllables to be clipped before the receiver audio is unmuted (is heard).
An infrared blaster (IR blaster) is a device that relays commands from a remote control to one or more devices that require infra-red remote control. For instance, it may also allow radio-frequency-based (RF) remotes (including those using Bluetooth) to control infra-red-based components.
Hence, the receiver frequency at the ground station must be adjusted higher to continue receiving the satellite. The satellite in turn, will be receiving the uplink signal at a higher frequency than normal so the ground station's transmitted uplink frequency must be lower to be received by the satellite. After the satellite passes overhead and ...
They are sometimes used to replace older infrared communication designs as they have the advantage of not requiring line-of-sight operation. Several carrier frequencies are commonly used in commercially available RF modules, including those in the industrial, scientific and medical (ISM) radio bands such as 433.92 MHz, 915 MHz, and 2400 MHz.