Patent GB-289649-A (GB)
IPC: G08B25/00
Filed: 1927-05-20
Abstract: 289,649. Siemens & Halske Akt.-Ges. May 17, 1927, [Convention date]. Fire, police, and like alarm systems and apparatus.-In a fire-alarm system the signals received at any district station may be automatically or manually re-transmitted to a central station in order that a second district station may be notified of an outbreak of fire in the event that the fire engine, of the station in the first district is already in use. Several district stations are connected to the central station over a common loop circuit. The Fig. shows one district station U<1> connected to the central station Z. The central station is connected to the district over a closed circuit from battery b<1>, line relay LRI, contacts of relay E<1> individual to district station U<1>, line wires, over the contacts of relays D, A and key G at the station U<1>, and through similar circuits at the other district stations over the contacts of the associated relays such as E<2>, E<6> to line relay LRII. A resistance R is connected across the line wires individual to each station so that when, for example, the repeater relay A is operated in the local alarm circuit e the line current is reduced to release the line relays LRI, LRII, and in consequence cause operation of the central station perforator Dlz and time. stamp St1. The signal received at the station U<1> may also be retransmitted manually in the event of notification of fire being received at the substation by telephone by operating a key C to connect the repeating relay D to the contacts KR of a transmitter. Operation of the relay A or D opens the short circuit across a locking relay II, which energizes and illuminates lamps T' individual to the district station. A thermostatic switch TK operated by the lamps T' energizes a relay J to prepare the circuit of an auxiliary lamp T<2> which is illuminated in the event of the transmission of a second signal before the central station lamp indications have been nullified, i.e. before the return of the fire brigade to station O<1>. The relay J opens the locking circuit of relay H to prepare that relay for subsequent operation. In the event of a second signal, the relay H illuminates the lamp T<2> over the contacts of the relay J. Upon the return of the brigade the key G is operated to insert into the line circuit a battery b<2> in opposition to the battery b<1>. This operation strengthens, the current in the corresponding relay K, which operates to cancel the indications displayed by the lamps T<1>, T<2>. A lamp La is illuminated upon the operation of one or other of the relays A, D to signify the absence of the brigade. Operation of the key G also cancels this indication. In the event of a breakage in the line circuit the relay E<1> is energized either automatically by the release of the line relay F or manually by the key Sd1 to connect the affected line to recording apparatus Dldx and to insert a resistance W in the loop circuit through the other stations. Signal transmission between the central station and the district stations is effected over a second loop circuit containing keys Ru<1>, Ru<2>, &c., which are individual to the district stations. Operating a key opens the line circuit and connects a transmitting apparatus N to the lines leading to the corresponding district station. A resistance WRu is also switched into the loop circuit to compensate for the resistance of the line leading to the district station. Signals from either the central station or the local alarm circuit are recorded at the district station on a perforater M, and signals transmitted to a substation from the central station may be automatically reverted to the central station over the substation transmitting loop circuit in order that confirmation of the receipt of a signal may be obtained. Telephonic, communication also may be. effected between the main station and the substations. The. midpoints of the line batteries and the individual loops are earthed in order to ensure satisfactory reception in the event of a fault on the line wires. An ammeter B connected in the line wires leading to each substation, indicates the state of the line.