the first public police telephones in britain were introduced in glasgow in 1891. these tall, hexagonal, cast-iron boxes were painted red and had large gas lanterns fixed to the roof, as well as a mechanism which enabled the central police station to light the lanterns as signals to police officers in the vicinity to call the station for instructions. as with chicago's boxes, the original intent was that trusted members of the public would be allowed access to the telephone in case of emergency using a special key that was registered to them, which would remain trapped in the lock until released by a master key carried by a policeman. a newer, rectangular type of cast-iron police box was introduced in glasgow in 1912, but with the signal light now powered by electricity rather than gas, and access to the telephone now restricted solely to the police.