498,563. Electric signalling systems. LANDIS & GYR AKT.-GES. Feb. 16, 1938, No. 4786. Convention date, Feb. 25, 1937. [Class 40 (i)] [Also in Group XXXIX] An alarm system comprises a transmitting station I connected by line j1 to a central station II of a network, which may be a telephone network, over which access is given to sub-stations III having audible or visual alarms S1, a sub-station being selected by a central station switch in response to impulses from the transmitting station which also transmits a control current to switch over the sub-station line from the normal central equipment to the alarm transmitting line j1 and to operate the sub-station alarm. The alarm is operated continuously or intermittently for a time predetermined by the transmitter. A certain impulse train causes all sub-station lines to be switched over to the alarm line. When impulse transmitter I is moved off normal, relay O pulls up, followed by P, and holds itself over cancel key B3 and contacts of a time switch R. Relay P connects line jl to the impulsing and control circuit, and G at the central station repeats the impulses to relay S2 which interacts with S3 to step the selector K. If an intermittent alarm is desired, key B1 is thrown to operate relays D and E which lock up, start the timing devices R, T, energize relay H and disconnect the continuous alarm key B2. Timing device T intermittently connects to line j1 one terminal of A.C. source E3 the other terminal of which is connected up by relay H. Relay W1 at the central station responds and on the first pulse V pulls up, locks over off-normal contacts k of the selector and operates the selected relay Y which switches the substation line over to the alarm line. Subsequent A.C. pulses operate sub-station relay W2 which switches in the alarm Sl. After a predetermined time, timing device R operates its contacts whereupon relays D, E, O and P fall back and the alarm ceases. Relay G at the central station falls back, the selector is stepped to normal, and the central station circuits restore. The timing devices R and T remain operated until R opens contact r1 whereupon relay H also falls back. If continuous alarm key B2 is pressed, relays D and F pull up instead of D and E, and the operations are the same as before except that the contact of T which applies intermittent A.C. is shunted by a contact of F applying continuous A.C. For a general alarm, digit 1 is dialled and X pulls up to release switching relays U whereby all the lines are connected to the alarm line.