A 900 MHz wireless transmission is a radio transmission at a frequency very close to 900 megahertz (MHz). These signals, which generally measure between 902 and 928 MHz, fall within the ultra-high-frequency radio wave band. This bandwidth is allocated to civilian unrestricted use in most countries and is often employed to provide wireless connectivity for small electronic devices, such as speakers or phones.
Radio signals occupy one portion of the electromagnetic spectrum. They are measured and rated based on the frequency with which waves propagate through space. One hertz is defined as one wave per second. Thus, a 900 MHz wireless transmission produces roughly 900,000,000 waves per second.
Most governments regulate the usage of the electromagnetic spectrum. This is done to ensure the most efficient use of bandwidth, a scare resource, and to guarantee that critical radio signals are not subject to interference from other radio users. 900 MHz wireless transmissions are generally relegated to the civilian sphere and, as such, can be used with few or no restrictions. In the United States, this bandwidth is allocated to amateur, advanced, general, and technical users.
Radio waves with different frequencies behave in particular ways when they interact with the environment. Signals in this specific range tend to travel relatively poorly through physical obstructions and do not often bounce off of either objects or the atmosphere. This property means that a 900 MHz wireless signal will not travel far through walls or other obstacles, making this type of signal a good choice for a variety of home electronics applications, as it is generally best if the signals from such devices do not transmit clearly into many neighboring homes.
Cordless phones are often manufactured to produce 900 MHz wireless signals. The limited range and generally good signal strength associated with this band make it an excellent choice for this application. It is relatively difficult to intercept the signal from cordless phones operating in this band, and breaking up their digital signals into multiple portions may further complicate the process of signal interception, offering excellent privacy. Some walkie-talkies use this frequency range as well, taking advantage of its relatively large size to offer many channels and good privacy features, in much the same manner as phones.
Many small household electronic items employ 900 MHz wireless transmissions. Wireless speakers can be located anywhere in a typical house and receive their input through radio waves, allowing cords to be dispensed with entirely. 900 MHz headphones that work in the same fashion are also available.