Personal Access Communications System (PACS) is a type of wireless telephone network compatible with telephone sets, answering machines, fax machines, and computers. A PACS can be used like a local area network (LAN) with voice capability and can be part of a larger network or can be connected into the telephone system.
A typical PACS resembles a cellular telephone network in miniature. It contains numerous radio port control units (RCPUs), each of which is the equivalent of a cellular repeater, but with a shorter communications range, linking subscriber sets within a radius of a few hundred feet. RPCUs are located on utility poles, atop buildings, and in other unobtrusive places that offer good coverage for several hundred feet in all directions. RPCU transmitter power is limited to 800 milliwatts. The operating frequency is in the UHF (ultra-high-frequency) radio range at 1.9 GHz.
The subscriber sets in a PACS can be fixed, mobile, or portable. Voice subscriber sets use 32 Kbps or 64 Kbps digital speech coding. Computer modems can be supported at speeds of up to 28.8 kbps or 57.6 kbps, respectively. Transmitter output power is limited to 200 milliwatts, but is often much less, on the order of a few tens of milliwatts. This low power level minimizes the likelihood of electromagnetic interference (EMI) to other electronic devices that might be located near the subscriber set.