Wiktionary
n. 1 (context chiefly British dated English) a telephone kiosk where members of the public may telephone the police; a few original boxes still exist in Britain, but they do not operate. Currently, the city of Glasgow (Scotland) has new police boxes, which are not booths but computerised kiosks, that connect the caller to a police CCTV control room operator. 2 a small community police station, a koban.
Wikipedia
A police box was a British telephone kiosk or callbox located in a public place for the use of members of the police, or for members of the public to contact the police. Unlike an ordinary callbox, its telephone is located behind a hinged door so it can be used from the outside, and the interior of the box is, in effect, a miniature police station for use by police officers to read and fill out reports, take meal breaks, and even temporarily hold prisoners until the arrival of transport.
Police boxes predate the era of mobile telecommunications; now British police officers carry two-way radios and/or mobile phones rather than relying on fixed kiosks. Most boxes are now disused or have been withdrawn from service.
The typical police box contained a telephone linked directly to the local police station, allowing patrolling officers to keep in contact with the station, reporting anything unusual or requesting help if necessary. A light on top of the box would flash to alert an officer that he/she was requested to contact the station. Members of the public could also use the phone to contact a police station in an emergency or, in the case of the Metropolitan Police, for assistance with any matter normally within the purview of the police.
British police boxes were usually blue, with the most notable exception being Glasgow, where they were red until the late 1960s. In addition to a telephone, they contained equipment such as an incident book, a fire extinguisher and a first aid kit. Today the image of the blue police box is widely associated with the science fiction television programme Doctor Who, in which the protagonist's time machine, a TARDIS, is in the shape of a 1960s British police box. In the context of a TARDIS, the image of the blue police box is a trademark of the BBC.
Usage examples of "police box".
So finally we telephone for help from a police box, and the ambulance comes and the patrol wagon too.
The big truck rolled around the corner of the warehouse and stopped by the military police box there.
A moment later there came a grinding of machinery, and the light on top of the police box began to flash.
Something else had appeared as well, an odd-looking blue police box.
The Doctor had explained to the organizers of the competition that the police box was a small part of his collection of thirties memorabilia.
It looked just as she remembered it from Kings Cross station and the Stone Mountain archives, right down to the words 'POLICE BOX' stencilled below the roof in white letters.
I could hear him snarling at me to let him go and not meddle in his affairs, but the words didn't make too much impression on me because all I could think about was that whatever it might look like from the outside, I knew perfectly well that this was no ordinary police box on Barnes Common.
He walked to the police box by the side of the road and struck up a conversation with the Kanaka policeman.
It looked like a police box, and Ace had had to look that one up, because the idea of a copper rushing around the corner to use a phone rather than a walkie-talkie was really strange.
Hand in hand with a strange little man, Chad was stepping into an old-fashioned police box.