Patent GB-688274-A (GB)
Title: Apparatus for checking the performance of patrols or tours of inspection by watchmenand the like
IPC: G07C1/20
Filed: 1950-03-03
Abstract: 688,274. Time-checking apparatus. NORFOLK, C. L. March 5, 1951 [March 3, 1950], No. 5441/50. Class 106 (iv). Apparatus for checking the performance of patrols comprises, at a master station, a control unit including means for providing different indications in response to respective electrical conditions of a line,-a timing device for rendering the means active at predetermined intervals and, at one or more selected localities on the patrol route, switches or other electrical components connected in the line and operable only at their respective localities to contribute to the attainment of one of the electrical conditions, the indicating means being responsive to a different electrical condition of the line for successive active periods so that for each active period all the switches or other components must be operated to attain the particular condition required for response of the means. In one embodiment, Fig. 1, apparatus for checking a watchman on patrol has a control unit at a central station comprising two indicator lights 18, 19, a counter 20, a timing device 21, a power pack, indicator relays 22, 23, a further relay 24 and a resetting relay 25. The system is completed by a line of two wires 26, 27 in which are connected in series route switches 28, 29 with pairs of contacts 28a, 29a in line 26 and 28b, 29b in line 27 such that when a pair of contacts a is closed the corresponding contacts b are opened. The power pack comprises a mains transformer 10, the primary 11 being fed from A.C. mains applied at terminals 12 and the secondary feeding a full-wave bridge-type rectifier producing 30 to 40 volts across the points 13, 14. Abbreviated symbols 16, 17 indicate connections to the points 13, 14 respectively. The timing device 21 may be a synchronous electric clock and controls contacts 21a which close when a watchman should begin one patrol and open when he should begin the next. At the end of one cycle the contacts are as shown in Fig. 1, contacts 21a then close, relay 30 is excited to close a circuit through contact 30c to excite relay 23 and also moves arm 30d on to contact 30f. Relay 23 causes switch 23b to close a circuit through lamp 18 which indicates the patrol is due to begin, switch 23c moves on to contact 23e to select the line 26 and contact 23f is closed. The watchman then throws all switches 28, 29 on his patrol route, opening contacts in the line 27 as he closes corresponding ones in line 26, when the last contact has been made the counter 20 is energized and also relay'24 which causes switch 24a to open and counter 20 to be de-energized, whereupon return springs advance the counter one step to register the completion of a patrol which is indicated at the same time by switch 24a opening the circuit through the lamp 18 and extinguishing it. The cycle is repeated in relation to the indicator 19 on the breaking of the contacts 21a and contacts of the relay 22 operate a similar sequence of those of relay 23, continuity being established on the line 27. When switch 15 is closed to put the apparatus in commission all the contacts will be closed on either line 26 or 27, if the timing device next closes contacts 21a in the former case or opens them in the latter case, relay 30 will be energized or de-energized and switch arm 30d will move over contact 30f or 30e to complete a circuit through relay 25 which will reverse switches 25b and 25c and cross lines 26, 27 so that lamp 18 will indicate when line 27 is selected and 19 when 26 is selected. This device prevents counter 20 from registering a patrol initially when no patrol has been made, In a second embodiment, Fig. 2, the control unit comprises a rotary selector switch with two banks of contacts 31, 32 over which operate wipers 31a, 32a, a timing device having contacts 33 which open for a short period each time a patrol is due to begin, two indicator lights 34, 35, a driving electro-magnet 36 for the rotary selector switch and a relay 37. The external line comprises two wires 38, 39 with route switches 40, 41. Successive contacts of the banks 31, 32 are connected to lines 38, 39, so that as the wipers move step-by-step the wires 38, 39 are selected alternately. If the wire 39 is selected as shown, the next opening of contacts 33 de-energizes relay 37 which opens switch 37a and closes switches 37b, 37c, whereupon lamp 35 indicates a patrol is due to commence, on patrol the watchman closes contacts 40b, 41b ... till a circuit is completed through relays 36, 37. After a brief delay, switch 37b opens and relay 36 is de-energized, whereupon the wipers 31a, 32a are stepped on to select the line 38 for the next cycle; switch 37c also opens and the lamp 35 is extinguished to indicate completion of the patrol and switch 37a closes to hold the circuit through relay 37 until it is broken by the timing device when the next patrol is due to begin, which will be indicated by lamp 34. A counter is actuated each time the driving electro-magnet 36 is deenergized and thus indicates the number of patrols completed.