The standard electrical dictionary : a popular encyclopaedia of words and terms used in the practice of electrical engineering / by T. O'Conor Sloane.

  • Sloane, T. O'Conor (Thomas O'Conor), 1851-1940.
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: The standard electrical dictionary : a popular encyclopaedia of words and terms used in the practice of electrical engineering / by T. O'Conor Sloane. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

    23/694 (page 17)
    ing of a window or door. As adjuncts to the system the treads of Fig. 9. Burglar Alarm Switch or Circuit Breaker. the stairs are sometimes arranged to ring the bell, by completing a circuit when trod on. Door mats are also arranged to close cir- cuits in like manner. For doors and windows switches are provided which are open as long as the door or window is closed, but which, on being released by opening the door or windows, automatically close the circuit. The circuit includes an alarm bell and battery, and the latter be- gins to ring and continues until stopped, either by the closing of the door or by a switch being turned. The connections are some- times so contrived that the reclosing of the door or window will not stop the bell from ringing.' The cuts show various switches for attachment to doors and win- dows. It will be seen that they normally keep the circuit closed, and that it is only open when pressure, as from a closed door, is brought upon them. In the case of a door a usual place for them is upon the jamb on the hinge side, where they are set into the wood, with the striking pin projecting, so that as the door is closed the pin is pressed in, thus breaking the circuit. Sometimes the connections are arranged so as to switch on the electric lights if the house is entered. Special annunciators show- ing where the house has been entered are a part of the system. A clock which turns the alarm on and off at predetermined hours is also sometimes used. The circuits may be carried to a central station or police station. One form of burglar alarm device is the Yale lock switch. This is a contact attached to a Yale lock which will be closed if the wrong key is used, completing a circuit and ringing a bell. Alarm, Electric. An appliance for calling attention, generally by ringing a bell. It is used to notify of water-level in boilers or tanks, of entrance of a house, or of other things as desired. It is evident that any number of alarms could be contrived. Alarm, Fire and Heat. An alarm for giving notice of the existence of a conflagration, Such are sometimes operated by si