Each Call Box is a battery-powered, solar-charged roadside cellular telephone. Call Boxes are easy to spot (bright yellow box on an aluminum post with a royal blue identifying sign) and are conveniently located next to highways and freeways. All Call Boxes are Teletype (TTY) equipped and usually placed in pairs across from each other approximately one to two miles apart, depending on availability of a consistent cellular signal, other motorist aid services, and ADA access.
In 2015, satellite Call Boxes were installed on select highways in San Bernardino County to supplement areas where there is inconsistent or no cellular signal.
The system of Call Boxes is operated in close coordination with both the California Highway Patrol (CHP) and the California Department of Transportation (Caltrans). A professional call answering center answers the Call Box calls, transfers them when appropriate, and public safety assistance such as law enforcement, paramedic and fire control are dispatched by the CHP when needed.