"Interoperability" is defined as "the ability for law enforcement and other public safety agencies to communicate among themselves." Interoperability has been impeded by incompatible radio systems, differing radio frequencies, jurisdictional concerns about information privacy, and a limited number of available radio frequencies. Until an ideal solution for interoperability is available, some agencies have begun cooperating to apply existing technology that "patches" radio systems together. BORTAC is one such patch. Resembling a hub and its spokes, the system is activated when one agency requests a patch to another agency. The dispatcher at the system's central location (hub) uses a mouse to connect the icons that represent the agencies. The voice transmissions come into the hub and are then transmitted through the spokes (phone circuits) to the appropriate agency, which remodulates the voice in a format compatible with its radio system. Under BORTAC, low band, VHF, UHF conventional, trunked, and 800 MHz systems can communicate directly with one another. Currently, BORTAC connects 16 Federal, State, and local public safety agencies in California's San Diego County. Its success prompted the development of RIO-Com, which connects 11 agencies in the Rio Grande Valley of South Texas. Cost per agency for a hub system that does not need to expand is from $3,000 to $4,000, not including monthly service charges.