Call box

Before the development of emergency telephone numbers and the proliferation of mobile phones, some firefighting agencies installed callboxes at various street locations so that a pedestrian or driver spotting a fire could quickly report it.

Call boxes also exist at regular intervals along the sides of many highways and rapid transit lines around the world, where drivers or passengers can use them to contact a control centre in case of an accident or other emergency.

[clarification needed] Roads in other places may have voice call boxes, though these are more expensive and must either be wired long distances, or rely on spotty rural mobile phone service.

The cost of callboxes for the Service Authority for Freeways and Expressways (SAFE) program in the San Francisco Bay area is $1.7 million annually.

[4] As a result, since 2009 approximately half of the callboxes have been removed from certain California highways, preferentially leaving them only in places where cell phone coverage is poor.

[7] Other voice call boxes use mobile phone service, and are solar-powered, so no wiring need be extended to the middle of a parking lot or other remote location.

Many callboxes can be programmed to be compatible with virtually any brand of VHF or UHF business band portable or fixed-base radio.

The system Harman envisaged was a series of telephone units in a box on a short post, spaced at 160-metre intervals (520 ft) along Perth's freeways.

Picking up the handset would trigger an alarm in the Main Roads control centre and police, fire or ambulance could then be determined by the caller.

Harman developed the system with the approval of the main roads commissioner and chief engineer, by adapting the existing design of communication facilities used at the security firm in which he worked.