Patent GB-1129161-A (GB)
Title: Improvements in or relating to supervisory circuit arrangements
Inventor: WOOD PETER
IPC: G21C7/36
Filed: 1965-05-28
Abstract: 1,129,161. Transistor circuits. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 26 May, 1966 [28 May, 1965], No. 22900/65. Heading H3T. [Also in Division H2] An alarm or protective arrangement for a plurality of like information channels, e.g. of a nuclear reactor, comprises a logic element associated with each channel, the elements being pulsed by a train of clock pulses and arranged to delay the pulses by an amount proportional to the number of defective channels or to remove a corresponding number of leading pulses from the pulse train. Fig. 3 shows an arrangement for three groups of channels or conductors A 1  . . . A 5 , B 1  . . . B 3  and C 1  . . . C 3 , the logic elements e.g. EL1 ... EL5 for each group being coupled to bi-stable switching devices BS 1  . . . BS 3  in a detector circuit OPD which in turn is connected to a discriminator DIS. A clock pulse generator (not shown), produces a train of pulses t 1  . . . t 9  of which pulses t 1 , t 3 , t 4 , t 6  and t 7 ; are supplied to the elements EL1 ... EL5, pulses t 2 , t 5  and t 8  are applied as interrogate pulses to the detector circuit OPD and pulse t 9  is a resetting pulse for the discriminator DIS. If all the conductors are in the correct electrical condition a train of output pulses is derived from each group of logic elements, the pulses being equal in number to the number of conductors, but if one or more of the conductors in a group are not in the correct condition then a corresponding number of pulses will be omitted from the front end of the pulse train derived from the group in question irrespective of the position of the defective conductor or conductors. Each bistable device BS1 ... BS3 is "set" when it receives a pulse from the associated group and the device BS1 is reset on receipt of a pulse t 2 , t 5  or t 8  to produce an output pulse to reset the device BS2 which in turn resets the device BS3 to produce an output pulse for the discriminator DIS. Thus when all conductors are effective, three pulses are applied to the discriminator DIS which produces an output at O/P1 to indicate 100% correct operation, but on failure of any one conductor in any group only two pulses are applied to the discriminator which then provides an output at O/P2 to indicate a "safe" condition. If only one pulse or none is received by the discriminator then no output is provided by the discriminator. The logic elements EL1 ... EL5, Fig. 4, each include a transistor TR and a square loop magnetic core with a winding MC(1) connected to the associated conductor, a winding MC(2) in a capacitor charge discharge circuit, windings MC(3), MC(4) connected in the transistor collector and base circuits and a winding MC(5) connected to a pulse source. When conditions are normal a pulse t 1  applied to element EL1 causes the core to switch to produce an output which triggers the transistor TR. The capacitor in EL2 charges and the pulse produced causes the core of EL2 to switch and produce an output pulse to trigger the transistor of that element. Thus an output pulse is propagated along the elements until an output is derived at O/P. When the transistor cuts off, the discharge of the capacitor resets the core. The logic elements DIS1 ... DIS4 of the discriminator are somewhat similar, Fig. 5 (not shown). In an alternative arrangement, Fig. 1 (not shown) each logic element includes a number of AND gates and a delay element which delays the transmission of a pulse by an amount equal to the interval between consecutive pulses.