Model_5_Point_Machines

MODEL 5 POINT MACHINES INSTALLATION, OPERATION AND MAINTENANCE OF MODEL 5 POINT MACHINES Model 5 A with series motor and pole-changer Model 5E with split-field motor Model 5P with permanent-magnet motor [pic] [pic] CONTENTS Page No GENERAL DESCRIPTION The motor 6 Friction clutch 7 Gearing 7 Operating and locking members 8 Point detector 9 MODEL 5A MACHINE The motor 13 Pole-changer 13 Superimposed detection 17 Typical wiring diagrams 18 Control circuits 18 MODEL 5E MACHINE The motor 19 Reversing switch movement 19 Typical wiring diagrams 19 MODEL 5P MACHINE Polarised contactor 21 INSTALLATION Lock rods and detector rods 21 Sleeper cutting 21 Soleplates 23 Wiring and connections 23 MAINTENANCE Lubrication 23 Care of commutator 25 Brush gear 26 Friction clutch 26 Lock rod. detector rods and connections 28 Pole-changer 28 Reversing switch movement 29 Polarised contactor 30 Point detector 32 General instructions 33 GENERAL DESCRIPTION The purpose of this handbook is to describe the operation and maintenance of the Models 5A. 5E and 5P point machines. The majority of the components are common to each type of machine, and though the three types are similar in appearance each has a distinctive motor and control circuit. The model 5A machine is powered by a series-wound motor and is reversed by means of an internal pole-changing switching mechanism. This reversing is done mechanically at the end of each operation, but coils are included to do the switching electrically if reversal in mid-stroke is required before the mechanical operation has been completed. The model 5E machine uses a series motor with split-field windings. The direction of rotation can be reversed by energising one field or the other through the reversing switch mechanism inside the machine. No pole changing coils are necessary for reversal in mid-stroke [pic] The model 5P machine has a motor with, a permanent magnet field. Control is effected by an internal polarised contactor that carries out all the necessary switching operations. Each of the three basic types of machine has a self-contained mechanism consisting of motor, gearing, operating and locking members, reversing mechanism and point-detector of the :" over-and-locked " type. The machines are designed to be supported on two sleepers and are suitable for operating single points or derails, single or double slip points or movable switch diamonds. An additional pair of points can be operated through rodding, if required. General views of the three types of machine are shown in fig. 38, 39 and 40. [pic] The motor is housed in a separate weather-proof case which is bolted direct to the point-machine frame. The same fixing arrangement is used for all motors. The motor drives the mechanism through a bevel pinion, crown wheel and friction clutch. The bevel pinion is keyed to the shaft of the armature, and rotates in plain self-lubricating bearings. The pinion-end housing and 4 Outline of motor for 5A and 5E point machine yoke consists of a single steel casting. The commutator-end housing has a cover fitted with a watertight gasket and a toggle fastener suitable for padlocking ; the cover gives easy access to the brushgear and ample space for commutator inspection. F i g . 4 shows the outline of a 5A (series-wound) or 5E (splitfield series) motor. These motors are of similar appearance internally. Fig. 5 shows the 5P motor, which has a permanent-magnet field. Friction clutch A friction clutch of the multiple plate type, as illustrated in fig.6, is included in the gear train to absorb the shock of starting and stopping, and also to prevent stalling of the motor in case of an obstruction in the points or failure to the machine to complete the locking movement. Gearing Different gear ratios are required for motors of various 3 voltages but no change to the machine frame is necessary when changing the ratio. The gears are shown n fig. 6. 7 and 8 ; only those shown in 6 and 7 require changing when the gear ratio is changed, that in fig. 8 being used for all ratios. 5 Outline of motor for 5P point machine [pic] [pic] Operating and locking members The throw bar, shown in fig. 9, is of ample size and strength. It is driven by a stud on the main gear (fig. 8). A coupling (fig. 10) is provided for attaching the throw-rod connection, and this may be bolted to either end of the throw bar to suit right or left-hand operation. [pic] [pic] Where the throwbar slides through the main frame there are hardened steel gibs which can be renewed when worn. The locking bar, shown in fig. 11, carries the locking dogs (which lock not only the lock rod but also the throwbar), and also releases the point-detector movement. The locking bar operates the pole-changer contacts after the machine has been operated and locked. Point-detector The point-detector contacts and movement are shown in fig. 12 and 13. The detector is of the "over-and-locked " type ; that is, the points must be thrown and locked before the point-detector contacts are closed. The lock rod and detector rods must be in their proper positions, either normal or reverse, before the moving contact member can operate to close or open the appropriate contacts. Operation Fig. 13 shows the point-detector movement and principal parts in positions occupied when the points are locked in the N O R M A L position. Plate H is rigidly fastened to the machine frame, and yoke Y is hinged at point K , being forced downward by spring S. The ends of yoke Y are attached to contact member B by means of pin J . Rocker F is rigidly fastened to contact member B and arms E and E l ,fig. 17) are fastened to the lock rod. Roller R, a part of contact member B. operates in and out of a slot in the locking bar. The operation of the point-detector is shown in Fig. 14. In the first stage of the ': unlocking ;* movement roller R is forced into the slot in the locking bar, which forces the contact member to the central position. This can clearly be seen b y reference to items 1A. IB and 1C in fig. 14. This movement opens all normal and reverse contacts, and closes all shunt contacts. As the points complete their stroke and the locking bar moves back to lock the points in the [pic] [pic] REVERSE position, the slot in the locking bar frees roller R. Then, as the point-detector rods reach their full REVERSE position, the left-hand rollers on contact member B drop into depressions in the detector rod as shown in 2C under pressure of spring S. This closes the full REVERSE contacts. Roller R assumes the position shown in 1C. Unless the lock rod has in the meantime moved to its full REVERSE position, arms E and E l by engaging rocker F (as [pic] Shown in items 3A. 3B and 3 C will prevent movement of contact member B from the central position. Thus, unless all detector and lock rods are in place and operative. contact member B of the point detector will stay in the central position, holding open all NORMAL and R E V E R S E contacts. Hand operation If it becomes necessary to operate a point machine by hand, a crank handle (fig. 15) is inserted into the friction clutch shaft through an opening covered by a plate in the gearcase cover. Before the crank handle can be engaged it is necessary to open a contact which is included in the motor circuit. As the handle is being inserted the contact is broken by sliding the cover plate to one side : the contact cannot reclose until the crank handle is removed. Two types of cut-off contact are supplied ; one. which requires manual reclosing by pushing back the cover plate, and the other which recloses automatically by a spring after the handle is removed [pic] Motor The motor is series wound and controlled through a pole-changing mechanism inside the machine. It is a four-pole motor, the poles being built up from laminations and each secured to the yoke with two bolts. The field coils are wired with pairs connected in series and four leads are brought out to a terminal block mounted in the commutator-end housing. Pole-changer The pole-changer contacts and movement are shown in fig. 13 and 16. These are operated mechanically by the combined action of locking bar and lock rod or electrically (in mid-stroke only) by pole-changer coils. These contacts control the current to the motor and pole-changer coils. [pic] [pic] Operation of pole-changer Fig. 13 a n d 17 illustrate the operation of the pole-changer. In the first part of the " u n l o c k i n g " movement of the machine, contact block T is centralised by means of crank N (on bracket M). This moves in slot C in the locking bar and is released by lock dog L moving away from plunger P which is supported by bracket E mounted on the lock rod. Lock clog L also moves out of the normal notch in the lock rod. thus unlocking it. When the point-throwing movement begins, the lock rod moves across ; plunger P is moved away from roller X on bracket M and is pushed back, as it passes wing V, to a position where it is held by a simple ball and spring latch. Similarly a t the end of the movement, plunger P I is moved into a position in line w i t h roller X I . During the " relocking " movement lock dog L moves back, this time into the reverse notch in the lock rod, thus re-locking it. In the final movement lock dog L forces plunger P I out of its latched position and against roller X I . and as crank X is no longer held in slot 0 this forces bracket M to its reverse position. Bracket M carries contact block T over to the reverse position and at the same time engages the wing on the arm U which moves contact block W to its reverse position, thus closing motor-controlling contacts Xos. 6 and 8 (fig. 18) i n readiness for the return movement. As will be seen from fig. 18 the centralising of contact block T closes the coil-controlling contact No. 4 but does not affect the motor-controlling contacts o n contact block W. If, however, it is desired to reverse the motion of the machine in mid-stroke, the normal control wire can be energised ; this will then energise the normal pole-changer coils through contact No. 4, and pull contact block W to the normal position, close motor-controlling contacts N o . 6 and 8, and reverse the direction of rotation of the motor. Operation of pole-changer by link motion When a machine is used without a lock rod, as for instance on trailing points, the pole-changer is operated by the movement of the throwbar through a link motion. (See fig. 19). The l i n k motion consists of two levers A and B pivoted on studs riveted to the cast base of the machine. The levers are connected at one end by a cross-member C on which are mounted two plungers P and P I corresponding to the plungers on the lock rod in the standard facing point machine. The two levers extend forward to the throwbar and ensase two studs D and D l mounted o n it. When the throwbar throws the points, these studs drive the levers and through them the plungers P and PI which operate the polechanger movement in the manner described on oage 13 for the machine with lock rod. [pic] As the link motion causes the cross-member C to move in the direction opposite to that of the throwbar. it will be apparent that the normal and reverse control wires are interchanged as compared with the machine with a lock rod. [pic] Superimposed detection When a.c. point detection is used with a d.c. point machine the extra apparatus mentioned below is sometimes provided as a means of superimposing the a.c. point detection circuit on the d.c. control circuit. This system has the following advantages : (a) after each operation of the machine the control wire for the next operation is proved (b) no additional wires are necessary for detection purposes between the controlling lever or relay and the point machine. The wiring diagram for a point machine using this system of detection is shown in fig. 30. The additional apparatus required when using superimposed detection is as follows : At the machine (a) A cast-iron box bolted to the end of the machine and containing one fixed resistor and one transformer. (b) A resistor mounted in the machine. At the control point (c) A reactor. A machine fitted with this additional apparatus is termed an A end n machine. If two machines are used, e.g. for the two ends of a crossover, unless separate detection relays are required! only one " A end " machine is necessary, the other being then termed a " B end " machine. Typical wiring diagrams Two typical wiring diagrams for Model 5A machines are shown in fig. 29 and 30. The first is a circuit using separate point detection and the second is one where superimposed point detection is used. Control circuits A control circuit for a model 5A point machine with superimposed detection using a point contactor is shown enclosed in chain dotted lines in fig. 31. This contactor includes an overload relay and cross-protection relay. Fig. 32 is a control circuit using a pull-through lever frame. [pic] MODEL 5E POINT MACHINE Motor The motor is split-field series wound and is controlled through the reversing switch mechanism inside the machine. It is identical in construction with, and has the same field-coil terminal arrangements as. the motor for the machine. Reversing switch movement The reversing switch contacts and movement are shown in fig. 20. The mechanical operation of contacts is exactly the same as described for the pole-changer contacts as used on the 5A machine ; the poie-changer coils and the four contacts (block W) and arm U shown in fig. 13. associated with this part of the movement, are omitted. The motor is controlled by means of the four contacts shown in fig. 20. The operating sequence for the reversing switch movement is shown in fig. 21. In this instance moving block T has three contact bars for bridging the contact fingers. In the central position the two pairs of fingers on the right-hand side are energised simultaneously to permit reversal in midstroke. The control circuit for this machine using a double-pole contactor is shown in fig. 34. When the two contactors are in the de-energised position the point machine is completely isolated from the supply. The control circuit is so arranged that the current through the motor is reversed when changing from normal to reverse operation and vice-versa. This permits a simple snubbing circuit with two rectifiers to be used for the motor. The snubbing contacts are 3—4 and 5—6 as shown on this diagram. The motor control contacts are 1—2 and 7—8. Operation of reversing contacts by link motion As with the Model 5A machine the reversing contacts are operated from the throw bar by means of a link motion when no lock rod is fitted. The operating mechanism is shown in fig. 19. Typical wiring diagrams A typical wiring diagram including a separate point-detection circuit is shown in fig. 33. A.c. point detection superimposed on the d.c. control wires is not used with this machine. [pic] MODEL 5P POINT MACHINE The motor used for operating this type of machine has a permanent-magnet field and therefore no field windings are required. A polarised contactor, resiliency mounted internally, is used for control and snubbing the motor. Polarised contactor This is a self-contained device consisting of two contactors and one overload relay. The main contacts of the contactors are provided with magnetic blow-outs. The contactor is shown in fig. 22. Reference to fig. 35 shows that during the time both contactors are de-energised the motor armature is disconnected from the supply and is short-circuited through the snubbing resistance. The polarised point contactors are controlled over a two-wire circuit through contacts on the point detector. During the point throwing operation both these contacts are closed to permit reversal in mid-stroke, which is achieved by reversing the polarity of the two control wires. Typical internal wiring diagrams for the point machine and point contactor are shown respectively in fig. 36 and 37. The contactors are immune to 50-c/s a.c. operation up to 750 volts. The permanent-magnet motor is also immune to a.c. operation. INSTALLATION Lock rods and detector rods Lock rods and detector rods are supplied loose and can readily be installed on site. Usually the former are of the double type and the latter of the single type ; both types are adjustable. On the upper surface of each rod there are locating notches. When the notch on the lock rod is in line with the machined surface on the side of the case immediately above the upper face of the rod), the locking slot in the lock rod is in position to receive the lock dog. A similar method, illustrated in ng. 1-i. is used to show when the rods are in the right positions to allow the point detector to operate. Sleeper cutting The sleepers supporting model 5 machines should be cut two inches deep and of a sufficient width to support the machine, the shoulder of the cut being so placed that v.-hen the supporting lugs of the machine are brought against the shoulders, the machine will be correctly fixed with respect to the [pic] track gauge line. When the switches are mounted on a soleplate. the sleeper nearest to the motor end of the machine must be cut deeper by the thickness of the soleplate to allow for the difference on level between the two sleepers. Machines are usually fixed three feet from the gauge of the nearest rail to the centre-line of the machine. Sole plates The soleplates should be fastened to the lugs of the machine on the track side with two three quarter inch dia. bolts through sleeper and soleplate. On the opposite side, the machine should be bolted to each sleeper with two three quarter inch dia. through-bolts. Wiring and connections Model 5 machines are assembled at the factory with all internal wiring (except for the point detector) in place, so that when installing the machine it is necessary only to bring in the outside wires and connect them to the appropriate terminals. Wires from the motor to the pole-changer are carried i n a duct running under the frame of the machine. Typical internal wiring diagrams of point machines are given in Figures 29. 30. 34. 36 and 37. M A I N T E N A N C E Lubrication The shaft bearings of the machine should be lubricated with good quality Medium or light grade machine oil. Where extremes of temperatures are to be expected a light oil should be used in winter and a medium oil in summer. The gear bearings are fitted with easily accessible, wick-feed oilers, which should. With one filling of suitable oil. lubricate the machine for several weeks. The motor is fitted with porous bronze bearings which hold sufficient oil for several years' service. E x t r a oil can be applied to these bearings but this should be done only when a motor is removed for cleaning and servicing. If the motor Gearings are oiled too frequently the lubricant may find its way to the commutator and cause sparking at the brushes. In older mode-s the lower ends of the clutch shaft and intermediate sear shaft are oiled through an oiler located in the upper end of the intermediate gear shaft. This shaft is hollow and oil is conveyed to the lower clutch bearing through a tube in the bottom of the main frame. [pic] In newer models the upper and lower bearings of the clutch shaft and intermediate gear shaft are each lubricated through separate oilers. The oiling point in the end of the intermediate gear shaft still provides oil for the lower bearing and the lower bearing for the clutch assembly has a separate oiler at the side of the main case. Through the hole in the main gearwheel oil should be also applied to the driving rollers. If the hole is not accessible the machine should be cranked until the hole is exposed. Small pin and pivot bearings should be given a drop of o i l occasionally where these are not accessible, oil holes leading to them have been provided. The faces of gears and heavy sliding parts should be lubricated with a good quality grease. [pic] Care of commutator The commutator should be kept clean by occasional rubbing with a lint-free cloth, or preferably with a small chamois skin, moistened with a little trichlorethylene. After a point machine has been in service for a few months the motor commutator should become dark in colour and highly polished. Sandpaper or emery cloth must never be used on commutators. If it should become necessary to re-dress the commutator, the armature should be removed and the commutator turned down in a lathe, using a very sharp diamond-point tool with a cutting speed of 400 ft./mm. a feed of 0.002 in t o 0.004 in per revolution and a depth of cut of 0.0005 in to 0.002 i n. After the face of the commutator is turned down it should be polished preferably with fine glass-paper, and the mica between segments cut down slightly below the surface of the copper. This should be done by one familiar with this class of work. Any dust remaining should be thoroughly cleaned off. Any accumulation of carbon dust around the commutator end of the armature or in the brush holder must be removed. Brush gear The rocker arm carries two brush boxes arranged to give adjustable brush spring pressure. The rocker is capable of movement about the axis of the armature and is set on leaving the factory to give sparkless commutation. Only special brushes of a copper gauze impregnated type should be used these have been found to give the best results under the conditions of normal, running, and " snubbing " at the end of an operation. Brush tension ma}- be adjusted to compensate for wear by unlocking and turning the knurled wheel on the brush gear. Tension should be maintained at 2 to 2 half lb per brush. The brushes should be renewed before they are worn down to the limit of the pressure arm ; new brushes must be carefully bedded before the machine is restored to service. The brushes must slide freely in the holders and be well bedded on the commutator. If they do not seat firmly on the commutator they should be bedded in by placing a strip of No. 00 emery cloth under the brush and around the commutator with the abrasive side to the brush. Hold the cloth firmly to the commutator, and rock the armature back and forth until the brush is properly bedded. Friction clutch Friction clutches should be tested occasionally to see that they are functioning properly. The clutch should be so adjusted that i f the throw bar becomes blocked the current taken by the motor with the clutch slipping is approximately 25% higher t h a n the maximum current during normal operation. To adjust the friction clutch proceed as follows: (a) Loosen the set-screw C. (fig. 6) that locks the adjusting nut. (b) Pass a five sixteenth dia. pin through the hole A in the bracket (fig. 25) and into one of the holes in the adjusting nut D. (fig. 6). [pic] (c) To tighten the clutch, insert the crank handle provided and turn counter-clockwise ; to loosen, turn clockwise. If the clutch is so loose that the friction is not sufficient to tighten the adjusting nut, it will be necessary to rotate the clutch body until the friction has been increased enough to permit adjustment with the crank handle. (d) After final adjustment tighten set-screw C. Lock rod, detector rods and connections The operation of lock and detector rods is described on page 21. Connections from :he points to the lock rod and detector rods should be as direct as conditions permit, and the method of connection should be such that lost motion is reduced to a minimum. Detector rods should be so attached to the point tongues that "rolling" of the points will have the least possible effect on the final positioning of the detector rods. To remove detector rods from the machine proceed as follows: a) Operate the machine by hand to the unlocked position. [pic] (b) Remove arms E and E l (fig. 17) from the lock rod. (c) Disconnect the lock or detector rod from the point connection and remove lug 11 or 12 and nuts 13 or 14 (fig. 26). (d) Withdraw the lock rod or detector rod from the machine. Figure 26 shows the arrangement for a single facing point. For double slip points and movable switch diamonds the lock and detector rod layouts may vary according to individual requirements. Pole-changer The mechanical pole-changer movement of the Model 5A machine is assembled as a unit (see fig. 16), and can be removed by first taking out the contact blocks and then unscrewing the four screws that hold it to the shelf in the contact compartment. This can be done without disconnecting any wires. Contact springs on the pole-changer can be removed by slackening the terminal nuts and lock nuts and pushing the spring back until it is unhooked from the square base of the terminal. The contact pressure should be between 6 and 9 oz. The stop fitted to each contact, spring should be so set that it is approximately in the middle of the loop in the contact spring when pressure is applied by the moving contact. The contact surfaces of the contact springs and the movable contacts should be kept smooth and wiped occasionally with a piece of lint-free cloth moistened with oil. After removing the core plate from the outside of the contact compartment, the pole-changer coils can be pulled out through the aperture after first disconnecting coil leads from their terminals. The pole-changer movement is operated by plungers P and P I (fig. 17) carried by arms E and E l attached to the inner lock rod. When adjusting the plunger screws, care should be taken to limit the adjustment so that no undue strain is placed on any part of the pole-changer. There should be approximately in of lost motion in contact block T (fig. 16) when the machine is fully locked in either position. Periodic tests should be made to see that the magnetically-operated member of the pole-changer will follow the lever. This test can be made in the signal box by operating the lever, and, before the point movement is completed, returning the lever to its original position. If the machine follows the lever the pole-changer is functioning properly. Tests should be made for b o t h the normal and reverse movements. Reversing switch movement The reversing switch movement (fig. 20) of the Model 5E machine can be removed in a similar manner to that described for the pole-changer movement used for the 5A machine. The pole-:hanger coils and contacts are not necessary on the reversing switch movement but the operation and adjustment of the mechanism and contacts is the same as that described for the pole-changer. Polarised contactor To remove the contactor (fig. 22) of the 5P machine detach the plug coupler and remove four nuts at the resilient mountings. Any servicing of the contactors should be carried out in the maintenance workshop. Easy inspection of contacts is obtained through the cover, but if maintenance work is necessary the whole unit should be withdrawn from its case by removing the eight screws holding the insulated panel Operating contactors Two operating contactors, as shown in fig. 27. are used for controlling the motor. The front contacts are adjusted in the factory so that a gap of 0.03 to 0.035 inch exists at the residual p in of the top pole when the contacts just make ; this ensures the correct contact wipe being obtained. When the contactors are de-energised there should be a gap of between 0.188 and 0.219 inch at the front contacts. [pic] The moving contacts should not require adjustment in service but if the fixed carbon contacts are burnt these can be renewed easily. To remove the upper contact loosen the screw holding the clip, which can then be moved to one side for fitting a new contact. The lower contact can be removed by unscrewing the nut on the central stud. See that the contact gaps are as given in the preceding paragraph when new contacts are fitted. Overload relay The overload relay is shown in fig. 28. This relay has two coils, one being an overload coil and the other a holding coil. The overload coil is connected in parallel with the thermal resistance unit that carries the motor current. If the motor takes excessive current due to a sustained overload this thermal unit becomes heated and increases its resistance thereby causing the overload to trip through the extra current passing through the relay coil. The relay is set to trip in 10 to 20 sec with a current of 12 amp. MODEL 5 POINT MACHINES No adjustment of the tripping time should be necessary but if this is desired two methods of adjustment can be made. The first is to move the outer bands of the thermal unit. If the bands are moved towards the centre, the tripping time will be increased ; if they are moved outwards, the time will be reduced. The other method of adjustment is by means of the return spring of the relay armature. If this spring is tightened the tripping time will be increased, and vice versa. When resetting the overload relay the contactor should be connected to a d.c. supply so that current can be passed through the overload coil. The current should be adjustable by means of a rheostat. To pass current through either section of the overload coil use terminals PM1 and B110 or PM2 and B110 with the appropriate main contactor held in the energised position. When the current is switched on it should be held steady at 12 amp through the rheostat, and the time measured for the overload relay to pick up. If the tripping time is not correct the value can be adjusted as described i n the preceding paragraph. If several readings are necessary a period of time should be allowed to elapse between each to allow the thermal element to cool. [pic] After making adjustments to tripping time, the holding coil operation should be tested. This coil should be energised by taking leads to terminals R W R and the moving contact to which the other end of the coil is attached. The voltage applied between these two leads should be adjustable and the pick-up and drop-away measured. For 50-volt contactors the pick-up should be 34 to 38 volts and the drop-away 12 to 24 volts. The operating values for this coil which has no separate adjustment, are not critical since its purpose is only to hold the overload relay energised after the relay has picked u p through an overload current. If the pick-up and drop-away are outside the values given this indicates that the pressure of the armature return spring has been set too high or too low as the case may be. Re-adjustment of the spring and also of the thermal unit will be necessary. The following contact settings apply to the overload relay. Contact A relay de-energised at 0.05 to 0.055 amp. Contact B relay energised at 0.03 to 0.033 amp. Contact pressure at B to be 1 half oz minimum. If necessary the contact pressure at B can be adjusted by bending the contact spring with suitable smooth pliers. Point detector The mechanical point-detector movement (fig. 12) can be removed after taking out the four screws that hold the movement to the shelf in the contact compartment. It is not necessary to disconnect any wires. General instructions After making adjustments, the machine should always be operated by hand to verify that it will operate properly without undue strain on any part ; it should then be operated electrically. The machine must be kept properly lubricated, and oil must not be allowed to accumulate in the machine housing. Care should be taken to keep wires, coils, friction clutch etc. free from oil . All terminal nuts must be kept tight. All bolts, nuts and screws must be kept tight: cotter pins should be in place and properly spread. [pic] 31 Point control circuit for d.c. operation with superimposed a.c. point detection. For a control using separate point detection, omit reactor and point detector relay. Terminals A and B must then be linked as shown dotted [pic] Point control circuit using controller on pull through lever frame with super imposed a.c. point detector relay. For a circuit using separate point detection, omit reactor and point detector relay. Terminals A and B must be linked as shown dotted. [pic] [pic] [pic] [pic]