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A police code is a brevity code, usually numerical or alphanumerical, used to transmit information between law enforcement over police radio systems in the United States. Examples of police codes include "10 codes" (such as 10-4 for "okay" or "acknowledged"—sometimes written X4 or X-4), signals, incident codes, response codes, or other status ...
Project 25. Several hand-held Project 25 radios used around the world. Project 25 ( P25 or APCO-25) is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications ...
These frequencies are known as the ISM bands (Industrial Scientific and Medical bands). The return signal of the tag may still cause interference for other radio users. [citation needed] Low-frequency (LF: 125–134.2 kHz and 140–148.5 kHz) (LowFID) tags and high-frequency (HF: 13.56 MHz) (HighFID) tags can be used globally without a license.
A scanner (also referred to as a radio scanner) is a radio receiver that can automatically tune, or scan, two or more discrete frequencies, stopping when it finds a signal on one of them and then continuing to scan other frequencies when the initial transmission ceases. The term scanner generally refers to a communications receiver that is ...
A trunked radio system is a two-way radio system that uses a control channel to automatically assign frequency channels to groups of user radios. In a traditional half-duplex land mobile radio system a group of users (a talkgroup) with mobile and portable two-way radios communicate over a single shared radio channel, with one user at a time ...
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz ). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio ...
Barcode reader. A stationary barcode scanner for a conveyor line. A barcode reader or barcode scanner is an optical scanner that can read printed barcodes and send the data they contain to computer. [1] Like a flatbed scanner, it consists of a light source, a lens, and a light sensor for translating optical impulses into electrical signals.
Radio frequency. Radio frequency ( RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency [1] range from around 20 kHz to around 300 GHz. This is roughly between the upper limit of audio frequencies and the lower limit of infrared ...