643,908. Electric elevator systems. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Jan. 15, 1948, No. 1282. Convention date, Jan. 15, 1947. [Class 40 (i)] In an elevator system in which the cars are divided into two groups, one of which serves primarily the upper floors and the other the lower floors, congestion in one zone automatically brings in a car from the other zone if conditions in that zone allow. The embodiment described is concerned particularly with the evening rush in a building of seven floors (including the ground floor which for convenience is referred to as the 1st). Two cars A, B, the circuits of B not being shown, are allocated to the low zone and are despatched from the ground floor at regular intervals. They do not take in " up " traffic at the ground floor and do not answer " up " landing calls. If, when' one of them starts, a predetermined quota of " down " calls exists in the low zone, the car proceeds to the landing corresponding to the highest of these and then descends answering all " down " calls on the way. If fewer than the quota of calls exist in the low zone when the car starts, it proceeds into the high zone and if it reaches the top floor is despatched as if it were a high zone car and then descends answering all " down " calls on its way. If the low zone quota of calls is reached while the car is moving up in the high zone, the car stops at the next landing at which there is a " down '' call or, if there are no down calls above it, at the next landing, and then reverses and proceeds to the low zone ignoring all other high zone calls. If the quota is reached with the car moving down in the high zone, the car ignores subsequent high zone calls. The quota for any low zone car depends on how many low zone cars are away from the ground floor. For instance, if two unanswered low zone calls are necessary to produce quota control of a first car, three may be necessary to produce quota control of a second before the first has reached a predetermined point on its return journey. Similarly, in a system with more floors and more cars, six calls might be required to give quota control of a third car. Two cars C, D, the circuits of D not being shown, are allocated to the high zone. They may start from the top floor at regular intervals and return immediately from the ground floor or may start at regular intervals from the ground floor and return immediately from the top. They may be organized to operate " high call reversal," but this facility is not provided in the circuits described. Under congested conditions, when a low zone car is byepassing " down calls in its own zone, the normal arrangement by which high zone cars byepass calls in the low zone is disabled. If a high zone car is byepassing calls in its own zone, a low zone car, unless it is already under quota control, is controlled to travel to the highest " down call in the high zone and then reverses, answering all " down " calls. Alternatively, if there is a low zone car at the top floor when the high zone congestion arises, it is controlled to answer the high zone calls instead of a low zone car from the ground floor. Corresponding relays in the circuits of the cars B, C, D have the same reference characters as those of car A with the addition of a prefix B, C or D to denote the car. Normal operation of high zone car C. With the car at the ground floor, " up " direction preference relay CW is energized by the release of " down " direction preference relay CX by a limit switch C30B. When the door of the car is closed, CDR operates and on a momentary operation of the starting switch CCS, the car is driven in the ordinary way. If any " up " calls are registered at the landings by buttons 2U ... 6U or if one of the car buttons C2c ... C6c is operated, stopping relay CS or CT is energized in the appropriate position and brings the car to rest with the aid of inductor relays CE, CF in known manner. At the top floor, the relay CW is replaced by relay CX which conditions the car to answer " down " calls by buttons 2D ... 7D on the return journey. On arrival at the low zone, however, CZ is operated and energizes byepass relay CPB which prevents the operation of CS so that landing calls in the low zone are not answered. Operation of high zone car with congestion in low zone. If either of the low zone cars has its button 27 operated to cause it to byepass calls, the operation of its relay PA or BPA energizes PE in the circuit of car C and this is followed by CPG which prevents the operation of CPB and causes the high zone car to answer low zone " down " calls. This action does not take place if the other high zone car has its relay DPG operated and so is already answering low zone " down " calls. Normal operation of low zone car A. The method of control is generally similar to that of car C, relays with a corresponding function having the same reference characters without the prefix C, but the stopping relay S only operates when the car is going down. No provision is made for answering '' up " calls and, provided that the " quota " of " down " calls in the low zone is not reached, the car goes to the top floor and then returns answering all " down " calls. Quota control. If there are two " down " calls registered in the low zone, enough current reaches relay Q, Fig. 5, for it to pull up and operate its helping relay QA which cuts in resistance to make Q quick to release. Under these conditions, if a low zone car is going up ( and provided that its relay TR is operated, as it is except under conditions of congestion in the high zone) its relay QM operates and releases Q by shunting it. If two (or more) low zone cars are out, the quick acting QM relay operates and the others are not operated until there are enough calls to energize Q in spite of the shunt. Relay K under control of wiper 34 and circuits 51 operates as soon as the car approaches a floor above which there are no low zone " down " calls or, failing this, on approach to the highest low zone floor. Similarly, if the car is already in the high zone, K operates over circuit 51A when the car approaches a floor above which there are no down calls. This is without effect in the circumstances of the previous paragraph but, with QM operated, causes J to pull up and lock and stop the car at the next landing. J also releases W, whereupon X pulls up to cause the starting switch to initiate downward instead of upward movement of the car. If the car is in the high zone, the energization of X is followed by that of the byepass relay PB which prevents the operation of stopping relay S by " down " landing calls until the low zone is reached, whereupon the operation of Z releases PB and all subsequent down calls are answered unless the car becomes full. The operator then energizes an alternative byepass relay PA. Operation of low zone cars with congestion in high zone. When a high zone car is full, its attendant operates its byepassing relay CPA or DPA (not shown). Provided that the low zone cars are not themselves byepassing, this energizes PF. Unless QM is already energized in the circuit of the next low zone car to leave (or that of a low zone car that has already started) TR of that car, which normally is energized shortly after the car starts and remains locked until its return, is prevented from locking or is unlocked and as a result, a subsequent energization of QM is prevented. As a further result, control of the ascending car is given to circuit 50 instead of circuit 51, 51a and the car thus proceeds to the highest " down '' landing call and reverses answering all " down " calls on the return journey. The operation of J to stop the car at the highest " down " call energizes PC which locks and is followed by PD. TR is then re-operated, but QM is still prevented from operating by PC. When Z pulls up on arrival at the low zone, PC is released and QM then pulls up if the number of " down " calls in the low zone has reached the quota of the car. If when high zone congestion occurs there is a low zone car at the top floor, PC in the circuit of that car operates immediately on the relapse of TR over floor selector contacts and is followed by PD and the re-operation of TR. PD is common to both cars and operates (or holds) TR in the other low zone car to maintain it under quota control. As in the other case, the operation of QM in the first car is prevented until Z releases PC.