Patent GB-833785-A (GB)
Title: Improvements in or relating to detecting and indicating apparatus particularly for fire
Inventor: STONOR CHARLES RICHARD PAUL
IPC: G08B17/06
Filed: 1957-04-25
Abstract: 833,785. Fire, burglar and like alarm systems. SOUND DIFFUSION (AUTO-THERMATIC) Ltd. July 24, 1958 [April 25, 1957], No. 13252/57. Class 118 (1). A detecting and indicating apparatus is characterized in that individual detectors serving a given section of a site are connected in a ring circuit to a section alarm box and the section boxes are themselves connected in a further ring circuit to a central master selector box which indicates in which sector an alarm has been given. Referring to Fig. 1 a three-core cable 1 interconnects in a ring circuit a master selector box 2 and section boxes 3. These section boxes are of two different types (Figs. 3a and 3b) connected alternately in the ring circuit. From each section box a coaxial cable loop 4 interconnects detectors 5 which may be of the type described in Specification 822,470. An alarm at any section box causes equipment in a master selector box to search for and identify the section box at which the alarm condition exists. In the embodiment described the searching is done by a uniselector of the reverse acting type. Normal condition.-Relays RA and RB in the section boxes (Figs. 3a and 3b) are energized by current flowing from the black line to earth. In the master selector box (Fig. 2) the uniselector has its wiper on the first contact a in each bank and current flows through relays RC and RD via contact a in bank US2, sufficient to energize RC but not RD. The second windings of relays RE and RF are energized in series via the red line and the contacts rb1 in each section box. Alarm condition.-Assume an alarm in the second section box given by open-circuiting or short-circuiting the coaxial cable. Relay RA releases operating an alarm A, and reversing connections of relay RB which locks out. Contact rb1 interrupts the current of the red line. In the master selector box, relays RE and RF release due to interruption of the red line. If only one is released i.e. due to an earth on the red line the other is released by contact rf 3 or contact re1. Contact re3 then opens to disconnect current from all relays RA and RB. The circuit of the potential divider comprising equal resistors R1 and R2 is completed so that the centre point is equi-potential with reference to earth or the negative supply and current flows through contact a on bank US 1 to energize first winding of relay RH. Relay RK energizes relay RL and these two relays operate in turn to pulse a distant alarm (not shown). Relay RH operating completes the energizing circuit for relay RJ, which energizes the driving magnet DM of the uniselector and releases RH and energizes RM. As relay RH releases, slugged relay RJ releases slowly and releases DM allowing the uniselector to step to contact b, re-operating relay RH. Stepping of the uniselector wiper to the contact b releases relay RC which completes the black line circuit to reenergize the relays RA in the section boxes with the exception of the box giving the alarm. Contact rc5 completes the green line (the slugged relay RM holding rm3 closed) which supplies a holding current, but not an operating current to the other windings of the RA relays. As the uniselector wiper steps to contact b one side of winding 1 of relay RH is earthed and the relay energized, causing the uniselector to step to the contact numbered 1. Each of the. numbered contacts in bank 2 has a pair of lamps such as L associated with it and as the uniselector steps to the contact 1 the corresponding lamps and relay RD operate, releasing relay RH and effectively connecting the second winding of relay RD in the red line. A negative potential is thus connected to the relay RB in the first section box. Resistance R3 is connected across the winding of relay RB thus allowing both relays RB and RH to operate. Relay RB holds via contact rb3 and contact rb1 switches the red line through to the next box, the one in which it is assumed an alarm exists. Relay RH holds over contact rh2, and operates relay RJ which then operates the driving magnet DM. Relay RH releases releasing relay RJ and the uniselector steps to contact 2 leaving the first section box in its normal condition. As the uniselector steps to contact 2 an earth is applied via the red line to relay RB in the second box. Resistance R4 is short-circuit since the relay RA is released and the current through RB and RH in series is sufficient to operate relay RB but not relay RH. The uniselector ceases to step leaving the appropriate indicator lamps lit. Inserting a marker into the jack JS releases relay RD operating relay RH to restart the stepping of the uniselector. The stepping continues applying alternate negative potentials and earth to the red line until all other RB relays are reset. As the uniselector steps to the last contact relays RF and RE are re-energized from the last contact of bank US2 which is earthed via contact rg2. The last contact of bank US1 supplies an earth to relay RH which with the relay RJ operates to step the uniselector to the contact a. Relay RC then operates via bank US2 and releases the relay RG. Since contact rg1 is opened. relay RH cannot operate and the uniselector remains on contact ra. The slugged relay RM then releases and releasing relays RG, RE and RF. The contact re3 opens the black line allowing all the RA and RB relays to release whilst contacts rg1 and rf2 restore the negative connection over contact a of bank US1 to relay RH. The interruption of relays RH and RJ then causes the uniselector to start a check cycle. Check cycle.-If no further alarm has been given the uniselector will continue stepping until the second cycle is completed, the marker allowing the selector to step past the position causing the alarm. The uniselector returns to contact a where relay RC operates relays RE and RF remaining holding over their second windings. The relay RM releases and disconnects the first windings of relays RE and RF and the equipment is restored to its normal condition. If a further alarm occurs in another section box the uniselector steps round until it stops at the position giving the alarm where it is marked as before, the relay RM will then release operating relay RG and at the end of this cycle a second check cycle will be started. After resetting the alarm the relay RA may be reset by starting a check cycle manually with the key K.