Improvements in and relating to Electrical Alarms.
Year: 1897

page_text: COMPLETE SPECIFICATION.
Improvements in and relating to Electrical Alarms.
J, RUDOLF HETTMANN, Engineer, of 1, Kirchplatz, Mokran, Near Nicolai, Silesia,
in the Empire of Germany, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
This invention relates to that class of alarms usually attached to doors, windows
or the like, where the opening of the door or window causes the closing of an
electrical circuit, and rings a bell, or in any suitable manner gives the alarm.
This invention consists in providing within a recess in one edge of the door,
window, drawer or like article which it is desired to protect; the two electrical
terminals of a circuit connected by a spring contact which is displaced by the
closing of the door or window, and breaks the circuit, but which automatically
closes the circuit and operates the alarm when the door, window, drawer or like
article is opened.
One method of carrying this invention into effect is illustrated in the accom-
panying drawing, where a part sectional elevation of the lower half of a window
sash is shown. The wooden sash a forms an insulator to which two terminal
plates 66 forming part of an electrical circuit are attached, the wires ff leading
to a battery or other convenient source of current. Within the recess c¹ of the
sash a a pin c is placed, having a recessed neck about which a circular or other
suitably shaped contact ring g fits, and the said pin is backed up by a spring plate d
fixed to the other edge of the sash a, so that in a normal position the spring
causes the ring to complete the circuit. When the window is closed the upper
ledge of the sash comes in contact with the head of the pin c, and depressing that
pin against the action of its spring d breaks the circuit. A separate switch may
be used to throw the alarm out of operation when desired, but when this separate
switch is in circuit and the window is opened, the alarm is at once given by the
peg c forcing the ring 9 against the terminals bb in the manner herein before
described, thus giving the alarm by bell or other suitable device.
It is to be clearly understood that this device may be applied to doors, windows,
drawers, cases, or any article rendered safe by a closing action.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
1. In electrical alarms for doors, windows, drawers and like articles the provision
of two terminals of an electrical circuit in combination with a spring peg and
contact plate in a recess upon one half of the article as a means for completing
the electrical circuit and giving the alarm when the article in question is opened,
and breaking the circuit and shutting off the alarm when the article in question
is closed, all substantially as and for the purposes hereinbefore described.

page_text: 2. The improved electrical alarm hereinbefore described with reference to the
accompanying drawing.
Dated this 24th day of September 1897
MARKS & CLERK,
Agents for the Applicant.