A signalling system for the use of the police in cities and towns has been recently exhibited in London by means of miniature apparatus. An ordinary lamp-post is furnished with a receptacle, in which is a clock dial and pointer, very much like the telegraph used in a steam-ship, only instead of the commands to 'Go ahead' or 'Go astern' the dial is furnished with notices of fire, robberies, riots and the like. A corresponding dial at the nearest police station synchronises with this on the lamp-post, and also gives the number of the lamp from which the message is sent. The plan is ingenious, and would no doubt be useful in many cases.
Chambers's Journal of Popular Literature, Science and Arts, 1890