system. Another source says system backbone equipment like consoles and base stations are expected to have a fifteen-year life. Mobile radios are expected to last ten years. Walkie talkies typically last eight. In a State of California document, the Department of General Services reports expected service life for a communications console used in the Department of Forestry and Fire Protection is 10 years. Two-way radio frequencies Typical two-way radios work on fixed radio frequency channels, though some can scan multiple channels in order to find a valid transmission. In an analog, conventional system, (the simplest type of system) a frequency or channel serves as a physical medium or link carrying communicated information. The performance of a radio system is partly dependent on the characteristics of frequency band used. The selection of a frequency for a two-way radio system is affected, in part, by: government licensing and regulations. local congestion or availability of frequencies. terrain, since radio signals travel differently in forests and urban viewsheds. the presence of noise, interference, or intermodulation. sky wave interference below 50–60 MHz and tropospheric bending at VHF. in the US, some frequencies require approval of a frequency coordination committee. UHF versus VHF The most common two-way radio systems operate in the VHF and UHF parts of the radio spectrum. Because this part of the spectrum is heavily used for broadcasting and multiple competing uses, spectrum management has become an important activity of governments to regulate radio users in the interests of both efficient and non-interfering use of radio. Both bands are widely applied for different users. Range The useful direct range of a two-way radio system depends on radio propagation conditions, which are a function of frequency. There are other factors that affect the range of a two-way radio such as weather, exact frequency used, and obstructions. See also TETRA (Terrestrial Trunked Radio) Astro (Motorola) Digital Mobile Radio PMR446 Family Radio Service GE Marc V Project 25 Quik Call I Motorola Saber Mobile radio Professional Mobile Radio Specialized Mobile Radio Mobile radio telephone Police radio Radiotelephony References External links Radio communications