FR2530232A1 - ELEVATOR SYSTEM WITH SPEED CONTROL APPARATUS - Google Patents

Abstract

A. ELEVATOR SYSTEM WITH A SPEED CONTROL DEVICE. B. ELEVATOR SYSTEM INCLUDING A DRIVE MOTOR 32 WHICH THE OUTPUT SHAFT CARRIES THE PULLEY 28 ON WHICH THE CABLE 26 GOES CARRYING THE CAB 12 IN THE ELEVATOR CAGE AND AN ENCODER OF POSITIONS 38 PROVIDING POSITION PULSES TO A CAB 42 CONTROLLER ALSO RECEIVING CALLS AND SENDING SIGNALS TO THE LOGIC OF THE LIMIT SWITCH ZONE 76 TO COMMAND 82, 90 AT THE SAME TIME AS A MEDIUM 52, 84, 86, 88 AND A MAXIMUM DEVIATION REFERENCE 92 AS WELL AS A MEANS OF MODIFICATION 94. C. THE INVENTION RELATES TO THE CONTROL OF THE SLOWING DOWN OF ELEVATOR INSTALLATIONS.

Description

"Elevator system with a speed control device"

  The invention relates to an elevator system comprising

  both a speed control device. Speed limit and control devices at the ends or end positions for an elevator car can adjust the level selector If the level selector does not work to give a normal slowdown, the system creates a auxiliary speed diagram for adjusting the end-of-travel slowing down In a known assembly for controlling an electromechanical level selector, there is a long cam placed in the vicinity of each limit switch. The cam opens a series of switches provided in the booth. elevator, one after the other

  as the cab approaches the end-of-travel level.

  If the level selector is working properly, for each cam-controlled "switch opening" in the elevator shaft, there will be a "switch closure" in the level selector crew. If this system fails, a auxiliary speed diagram

  is established for example by an electromechanical transducer

than activated by the long cam.

  Speed control and limitation devices in the vicinity of the limit switches can control the speed diagram generator when the elevator car approaches the end-of-travel level. An end-of-travel deceleration scheme is provided for at the end of travel. place of the normal deceleration pattern when a malfunction is detected so as to decelerate the cab to the final level However changes in the signal of the speed diagram generator did not enter the deceleration of the cabin if there has difficulty in the drive system Similarly the speed diagram generator can function properly but due to a difficulty in the drive system, the cabin may not decelerate along the desired path as it closer to the end-limit level Such a system takes no action and may allow the cab to move closer to the end of the race

with excessive speed.

  A speed control system that controls the speed of a cab according to the position of the cab can provide very great protection against

  approaching the end of the race at an excessive speed.

  U.S. Patent No. 3,779,346 discloses such a system which

  Continuously controlling the speed of the car according to its position when the car is approaching each level of destination.

  close together are provided in the elevator shaft in the vicinity of

  each end of stroke and cooperate with a sensor placed on the cab to give a permanent speed error signal, which is used in a reference circuit to detect overspeed. The speed error signal is also used in a circuit that generates an auxiliary deceleration scheme The auxiliary deceleration scheme replaces the normal scheme

  speed when an overspeed is detected.

  If the difficulty does not lie in the circuits giving the speed diagrams but in the drive, the generation of an auxiliary speed diagram will not be effective Thus this assembly is used with a low inertia, a speed sensor switch of a cabin operating rapidly as a support, such as the speed sensor described in US Pat. No. 3,814,216. If the cabin speed is excessive for the position of the cabin relative to the limit switch controlled by this

  speed detection switch, the cab is required

  emergency stop.

  U.S. Patent No. 4,084,323 discloses a system of

  non-continuous cab speed tread as opposed to the continuous cab speed control system according to

  U.S. Patent No. 3,779,346. This non-con-

  tinu controls the speed of the car according to its position at different non-continuous speed control points in the elevator shaft The speed of the car is compared to two reference speeds at least at the car position control points Si the cabin speed exceeds the lower reference speed but not the higher reference speed, the system tends to decelerate the cabin using a diagram

  auxiliary speed limit slowing down.

  If the cabin speed exceeds the higher reference speed at any checkpoint, the cabin

  is obliged to make an emergency stop.

  The main object of the present invention is to create an elevator system which is as effective as a non-continuous control system of the speed of the car without the need for a long adjustment of all

  separate control points placed in the lift cage

  and without reducing the number of checkpoints

  that the compromise -is found between the erroneous trigger

  and the late detection of exceeding the speed.

  For this purpose, the invention relates to a system for

  for a multi-storey building having a lower end-of-travel level and an upper end-of-travel level as well as an elevator shaft receiving an elevator car, a drive means for providing the elevator car, a

  control means for the drive means which

  the slowdown and stopping of the cabin at a destination level, the slowing down of the

  predetermined speed curve and having a predetermined slope

  completed, a first and a second reference placed in the

  elevator shaft in the vicinity of each level of

  nation defining respectively the upper end-of-travel zone and the lower end-of-travel zone and the distance to be traveled between any point

  and the corresponding end-of-race level, a trans-

  electromechanical conductor provided on the elevator car, implemented by the reference mark of each end-of-stroke to provide a first signal that decreases substantially linearly depending on the distance between

  the elevator car and the limit switch level cor-

  respondent, means providing a second signal corresponding to

  at the actual speed of the elevator car, at

  less when the elevator car gets closer to one -

  end-of-travel level in an end-of-travel zone, means for adjusting the slope and amplitude of the first signal in accordance with the predetermined speed curve and the predetermined slope of the normal end-of-travel deceleration, if there is a difference whose amplitude corresponds to any difference between the first and the second signal, a means giving a signal

  reference point corresponding to the maximum difference

  and a comparator to compare the difference signal

  the reference signal and giving a pre-

  determined when the actual difference-speed

  exceeds the maximum speed difference allowed.

  The present invention will be described in more detail with the aid of the accompanying drawings, in which FIG. 1 is a partially schematic and partially block view of an elevator system according to the invention. FIG. 2 is a partially schematic view

  and partially en bloc of an electromechanical transducer

  that can be used to give an electrical signal of which

  is the distance to the level of destination

nation or end of race.

  FIG. 3 is a schematic diagram of the functions

  in block form in Figure 1.

  Figure 4 is a graph of operation

  of the elevator system during a normal slowdown

  wrong and stop at a destination level.

  FIGS. 5A and 5B are graphs showing the operation of the elevator system during two different overspeed situations when the

  elevator car is getting closer to a level of destina-

  in the slowdown zone of destination or

limit switch.

  Description of various preferred embodiments:

  The present invention can be integrated into any elevator system to reduce the length and

  complexity of this description, it is assumed that the

  elevator system is that described in patents U S 3,713,011 and 3,750,850 Certain signals and circuits

  used in the present description and not shown

  in the patents referred to above, are described and

  represented in U.S. Patents 4,042,068 and 4,307,793.

  The drawings and in particular FIG. 1 show an elevator system 10 with an elevator car placed in an elevator shaft 14 to move relative to a building 16 having several levels. Only the lower end-of-travel level 18, the end-of-race level

  20 and an intermediate level 22 are

  1 elevator car 12 is suspended from a cable assembly 16 and a counterweight 27 Cables 16 pass over a traction sheave 28 carried by the axis 30 of a drive motor 32 as shown in FIG. by

  example, a DC motor mounted according to a system

  A power source for the motor 32 which consists of a drive control 34 and an AC potential source 36 is connected to the motor 32 via a contactor with an electromagnetic coil 7 C and

  contacts 7 C-2 An electromagnetic brake equipped with a

  bearing BK is provided so as to exert a braking force on the pulley 28 when the supply of the brake is cut off and to release the brake when the supply

of winding BK is established.

  A pulse wheel 38 is mounted to be driven by the movement of the pulley 28 or by a control pulley (not shown). A sensor 40 detects the movement of the elevator car 12 through

  to the orifices distributed around the periphery of the impulse wheel.

  38 orifices are spaced apart to give.

  a distance pulse for each normal increment

  moving the cabin; for example, there is an impulse

  for each 6-minute ride from the cabin.

  40 which can be of any suitable type,

  such as an optical or magnetic sensor provides the impulses

  The cabin control device 42 includes a level selector which maintains the position of the cabin at a level of the cabin control device 42.

hatching in response to the pulses.

  Elevator calls are recorded at the elevator push-buttons 44 in the cabin 12 as well as the push buttons of the elevator call.

  hall placed in the halls or landings of different -

  levels of the building such as the button

  push-up 46 level, destination 18, the

  push-button descent 48 at the upper limit of

  and the up and down push-buttons at each intermediate level. As described in detail in U.S. Patent 3,750,850, the cabin controller 42 includes a level selector which processes

  the distance pulses of the detector 40 for developing

  per information about the position of the cabin 12, in the elevator shaft 14 and the level selector also directs these distance pulses, processed to a speed diagram generator which generates a

  velocity reference signal to train the device

  command 34, giving in turn the tensio N of

  The level selector keeps track of the elevator car 12, the service calls of the car and provides the request for the acceleration signal to the pattern generator.

  speed and gives the deceleration signal to the gen-

  speed diagram at a precise moment

  to the cabin to decelerate in a decelerating

  The level selector also provides the auxiliary service control signals such as the door operating device and the lighting of the bearings; it controls the reset of the cabin call and landing call commands when a cabin call

or landing has been serviced.

  According to the teaching of the invention, the elevator system 10 comprises an electromagnetic transducer 52 carried by the elevator car 12 and which gives a continuous signal ECI of reduced amplitude when the cabin 12 approaches either the one of the end-of-run 18 or 20 levels of the end-of-run slowdown zone

  The transducer 52 may be the transducer

  The electromagnetic transmitter described and shown in U.S. Patent 3,207,265 which is used in this particular patent to provide a replacement speed scheme. The transducer 52 may also be the transducer.

  shown in detail in Figure 2 or any other trans-

  suitable electromechanical conductor that can be mechanically associated with the distance to be traveled by the elevator car to the destination level it approaches. The invention recognizes that electromechanical devices used heretofore to provide a replacement speed scheme can also operate to give a distance signal to be traveled and this distance signal to be traversed can further be processed and used in a switching arrangement of

  speed, accurate in solid state technique.

  The mechanical connection between the position of the cabin 12 and a destination level can be achieved by means of continuous marking in the form of cams 54 and 56 placed in the vicinity of the lower level and the

  level 18 and 20 respectively and a follow-up

  The cams 54 and 56 define the end-of-travel deceleration zones and thus, by their slope, each point of each cam is uniquely related to the distance between this point and the end-of-travel level. The transducer 52 may include an operating arm 58 connected to a lever 60 having a roller 62 positioned to contact the cams at the beginning of each end-of-travel deceleration zone. The cams 54 and 56 have slopes so as to turn the operating arms 58 about their axis in a way directly proportional to the distance

  separating the elevator car 12 from the destination level.

  The cams 62 and 63 of the elevator shaft 14 and the

  switches 64, 66 of the elevator car 12 or invert

  are provided to provide the PBOT and PTOP signals

  which are high or true when the driver's cabin is

  censor 12 is in the lower end-of-travel zone and in the respective upper end-of-travel zone. A limit slowing zone is defined as the distance during which the elevator car 12 must change from cruising speed and decelerate to a stop at the end of travel.

  corresponding to a deceleration program

  Thus, when a cabin 12 is in the lower end-of-travel zone, the signal PBOT will be high and the signal PTOP will be low When the car 12 is in the upper end-of-travel zone, the signal PTOP is high and the PBOT signal is low Both signals will be low when the elevator car 12 is in between

  two slowdown zones at the end of the race.

  Suitable means such as a tachometer 70 may be provided to provide a continuous signal of which

  the amplitude corresponds to the real speed of the cabin.

  As shown in FIG. 1, the tachometer 70 may be driven by the edge from the surface of the traction sheave 28 or else from a pulley

  trained to give a relatively noiseless signal.

  The solid state speed switching function will first be described from the functional point of view using the block diagram portion of FIG. 1, then a preferred embodiment will be

  described in detail with the aid of the remaining figures

  tachometer 70 called TACI, is filtered in a low-pass filter 72 which removes spikes and the like

  high frequency noise and a processed signal is applied

  than an absolute value circuit 74 giving a positive polarity signal regardless of the direction of

  moving the elevator car 12.

  The logic of the end-of-travel zone 76 is implemented by the direction of movement of the cabin

  represented by the signal 1 RL and 2 RL indicating the movement

  climb and descent respectively when this signal is true or high and the position signals of the cab of the LTOP end zone

  and LBOT which are logic level signals from the inter-

  face 78 corresponding to the respective power level signals PTOP and PBOT signals 1 RL and 2 RL are

  logic level signals responding to the <control relay

  up and down movement IR and 2 R res-

  US Pat. No. 4,042,068. A high or true EN authorization signal is provided when the elevator car is between the end-of-travel zones and when it is in an end-of-travel zone and is approaching the end-of-travel level signal EN is low when cabin 12 is in an end-of-travel zone and moves away from

  corresponding limit level The output of the cir-

  fired absolute value 74 and the authorization signal EN are both applied to a function of authorization 80 which gives an output signal responding to the TACI signal when authorized by the signal EN The output of the function

  80 is applied to a deviation detector.

or error 82.

  The output signal ECI of the electronic transducer

  52 is supplied to a low-pass filter 84.

  the amplitude of the conditioned signal represents the distance

  be the elevator car 12 and the destination level

  when the elevator car is in the slowdown zone

  End of travel signal The signal is then processed in function 86 to adjust its slope and intensity to match what is defined by the TACI signal when the elevator car makes a normal stop at 1 l.

destination level.

  When the output of the transducer 52 reaches the ex-

  lower end of its output range, this signal

  becomes non-linear and is thus blocked in the function

  88 when it drops to a predetermined value If no overspeed is detected when the elevator car reaches the position at which the signal is

  locked, it is known that the cab is slowing down.

  the normal end-of-travel

  Rated speed signal has no effect.

  The processed signals ECI and TACI are compared in the deflection detector 82 and any difference is

  applied to the comparator function 90

  reference 92 gives a reference amplitude to the

  90 indicating the maximum deviation allowed when the actual speed of the TACI booth exceeds the

  nominal speed or ECI setpoint speed If the deviation

  tion reaches the reference amplitude, the output of the com-

  parator 90 changes, and this change can be used to

  switching on or off according to the case of an ETS relay The ETS relay contacts are connected to a modifying means 94 The modifying means 94 can

  include the contacts of the ETS relay connected in a

  For example, a contact can be connected in such a way as to cut off the power supply of the contactor 7C, which cuts off the power supply of the drive motor 32 and connects the resistors.

  dynamic braking in the armature circuit as -

  c-ela is shown in US Pat. No. 4,307,793. A contact will also be connected to cut off the power supply of the brake winding BK to implement the

mechanical braking.

  Figure 2 is a diagram of an electronic transducer

  The mechanical transducer 52 shown in FIG. 1 generally employs a transducer 52.

  transformer 94 in which the coupling between the coil

  the primary winding and the secondary winding is adjusted

  continuous in response to the rotation of the operating arm 58.

  The transformer 94 has an E-type magnetic core with an E-shaped section 96 defining an inner branch and two outer branches and a section 1, with each section being formed.

  of a set of magnetic metal sheets

  The primary winding or input winding 100 may be placed around the inner leg and the secondary windings or output windings 102 and 104 are provided around the outer limbs. The actuating arm 58 may be attached to the I-shaped section. 98, this section I 98 rotating about the axis of the operating arm 58 The closely adjacent portions of the sections E and 1-have a shape such that when the section I, 98 turns from its normal position to ensure

  the maximum transfer of the flow to a trans-

  minimum flow rate, the output voltage that appears across the second-area windings 102 and 104 is

  linked in a virtually linear fashion to the

  In order to adjust the amplitude of the output voltage, the primary windings 100 may be

  connected to a source 106 of alternating voltage by the

  through an adjustable voltage autotransformer 108 -To give a unidirectional output voltage,

  the output voltage appearing at the terminals of the windings

  102 and 104 are straightened by means of a bridge

  rectifier 108; the rectified wave is filtered by an RC filter 110 to eliminate ripples and the resulting unidirectional signal is the ECI signal usable for the speed switching function in technique

solid state.

  Figure 3 is a diagram of the communication function

  The TACI signal of the tachometer 70 is first applied to a function 72 which may include an operational amplifier 112 connected as a low-pass filter. amplitude adjustment As the TACI tachometer voltage has a positive polarity when the elevator car moves in a direction and a

  negative polarity when moving in the direction of

  In contrast, the filtered signal TACI is applied to an absolute value function. The function 74 may consist of operational amplifiers 116 and 118 respectively connected as a precision rectifier and an amplifier-adder for the TACI signal to have a polarity. positive at the output of the function 74. The logic circuit 76 may comprise four double NAND gates (also called NAND) 120, 122, 124, 126, the NAND gate 126 being connected as inverter The LTOP and 2 RL signals are applied at the entrances of the NAND door 120; the signals LBOT and 1 RL are applied to the inputs of the NAND gate 122 The output of the NAND gates 120 and 122 is applied to the inputs of the NAND gate 124 The output of the NAND gate 124 is inverted by the NAND gate 126 If the cabin 12 is in the upper end-of-travel zone, and moves in the up-climb direction, the RL 1 up-shift signal and the LTOP upper end-of-travel signal will both be at logical level one while the Both signals RL and LBOT will be at the logic zero level, so that the gates 120 and 122 both apply a logic state one to the NAND gate 124. The NAND gate 124 thus outputs a logic zero state which is inverted into one. logical state one by the gate 126 Thus, the signal EN is high level that is to say it is in the authorization position A similar result occurs when

2530232-

  the cabin 12 is in the end slowdown zone of

  lower stroke and moves in the downward direction.

  If the elevator car 12 is in the upper end-of-travel zone downward, the gate 120 outputs a zero logic state and if the car is in the lower end-of-travel zone and moves upward, the gate 122 outputs a zero logic state Thus in each case, the output of the gate 124 will be high level and the output of the gate 126 will be low, which corresponds to the level of prohibition of the signal EN The function of authorization 80 may comprise an operational amplifier 128 connected as a means of

  locking and an operational amplifier 130

  as a non-inverting voltage follower.

  Operator 128 is connected by its inverted input to the output of the absolute value function 74, its non-inverted input being connected to receive the signal EN The uninverted input of the amplifier

  130 is connected to the inverted input of the

  operational plifier 128 A diode 132 is connected by its anode to the inverted input of the amplifier

  128 and its cathode is connected to its output.

  When the authorization signal EN is high again, the output of the operational amplifier 128 is high and the output of the follower 130 follows the output

  of the absolute value circuit 74 When the signal of

  EN is low, the output of the ampli-

  The operational flag 128 is low, which blocks the voltage applied to the operational amplifier 130.

  practically at the zero value Thus, the output of the am-

  operational plifier 130 has a positive polarity by following the absolute value of the TACI signal when the signal

  EN is high level and has a practical output-

  when the EN signal is low.

  The ECI signal of the electromechanical transducer 52 is applied to the signal conditioning function 84 which may comprise an operational amplifier 134 connected as a low-pass filter. The conditioned signal is applied to the processing function 86 which may comprise

  an operational amplifier 136 connected as an amplifier

  Inverter-inverter means are provided for selectively biasing the signal applied to the inverted input, for example an adjustable resistor 138 whose cursor is

  connected to the inverted input of the operational amplifier

  1 to 36 and whose terminals are connected to unidirectional sources of opposite polarity. The operational amplifier 136 is also connected so that its

  gain can be selected in an adjustable manner and

  the desired adjustment of the slope of the signal ECI for example with the aid of an adjustable resistor 140 provided in the feedback loop The adjustable resistors 138 and 140 are adjusted so that the amplitude and the slope are adapted to those of the TACI signal when the signal

  TACI responds to a normal slowdown at the end of the race.

  Since the ECI signal is non-linear when it approaches the zero value, its amplitude is blocked.

  as soon as it is reduced to a predetermined value

  This blocking is ensured by the function 88 which may comprise an operational amplifier 142 connected as a locking means and an operational amplifier 144 connected as a non-inverted voltage follower The output of the function 86 is applied to the inverted input of the operational amplifier 142 and

  its non-inverted ehtrée is linked to a reference

  which consists of an adjustable resistor 146 and a

  negative source of unidirectional potential Resistance

  adjustable rate 146 is set to select the

  negative voltage to which the ECI signal is to be blocked.

  When the signal ECI drops to the value chosen by the reference, the output of the operational amplifier 142 switches from the high level to the low level, which locks

  the voltage applied to the follower 144.

  As shown in the graph of FIG. 4, when the elevator car 12 performs a normal end-of-travel slowing, the TACI 'and ECII signals are substantially equal but of opposite polarity for each other.

  amplitudes for each distance to be traveled, incremental

  tale, up to the destination level Thus the difference or deviation between the signals of opposite polarity can be obtained by the addition function 82 which includes an operational amplifier 148 connected as an amplifier

  reversal adder If the actual speed of the-

  the cabin represented by the signal TACII exceeds the nominal speed or speed of the cabin represented by ECI ', the output of the operational amplifier 148 will be negative If the signal TACI' is lower than the signal

  ECI ', its output will be positive Thus, the function of com-

  Solid state velocity mutation is performed by a comparison function 90 which may be formed of an operational amplifier 150 and a reference 92. The reference 92 may comprise an adjustable resistor 152

  connected to a negative unidirectional potential source.

  Reference 92 is connected to the inverted input of the

  operational fold 150 and the output of the amplifier

  Operator 148 is connected to the non-inverted input

  of the operational amplifier 150 The output of the

* Operational plifier 150 can be connected to a terminal of the working winding of an ETS electromagnetic relay whose other terminal is connected to a unidirectional positive voltage source If the deflection does not reach the negative value chosen by the reference 92, the output of the operational amplifier 150 will be high and the ETS relay will not be energized If the deviation reaches the preset reference level which is chosen to represent a predetermined speed error

  for example 27 m / min, the output of the amplifier

  150 switches low and powers the ETS relay These contacts can be used to initiate an emergency limit stop as described above. Figure 4 also shows that-if the output of

  ECI transducer 'is blocked, the deviation becomes nega-

  it deviates from the maximum deviation reference. The deviation would also be positive if the EN authorization signal went low for

force the TACI signal to zero.

  FIG. 5A is a graph showing a first example of overspeed detection by the solid state technique speed switching function.

  example, the elevator car does not start for

  At the appropriate moment, the TACI signal 'remains

  constant while the signal ECI 'begins to decrease.

  When the difference between the amplitude of the signals is

  that is, the deflection of the output signal of the function 82 reaches the maximum deviation reference at point 154, which results in the initialization of an end-of-travel emergency stop. In another example according to FIG. 5B, the elevator car begins to decelerate at a suitable time but on a different slope from normal, the deceleration of the car being too weak The two signals thus deviate more slowly than in the first example but when the deviation reaches the deviation reference maximum point 156, an emergency stop of

end of race will be implemented.

  In summary, the above description is for a

  elevator system having a switching function

  speed in solid state technique that controls

  limit slowing down according to the distance of the elevator car from the destination level If the car speed deviates from the set speed by a predetermined value for any distance remaining at move, approaching the end-of-travel level, the overspeed condition is immediately detected and a signal is sent quickly to initiate the desired change

  the operation of the elevator system.

Claims (1)

R E V E N D I C A T O N S   1) Elevator system for a multilevel building with a higher end-of-travel level and a   lower limit and a cage of   a censor in which an elevator car moves, and a drive means for the elevator car and a control means of the drive means for controlling the slowing down and stopping of the elevator car at a destination level, the slowing down of the elevator car end normally defining a predetermined speed curve having a predetermined slope, characterized by first and second continuous tracking means in the axle elevator cage in the vicinity of each destination level, defining an upper end-of-travel zone and a respective lower end-of-travel zone as well as the distance to be traveled between any point and the corresponding destination level, a transducer   electromechanical system on the elevator car and   by marking each end-of-travel zone to give a first signal which decreases substantially linearly as a function of the distance between the   elevator car and the corresponding destination level   a means providing a second signal responsive to the actual speed of the elevator car at least when   the elevator car is approaching a level of desti-   nation in an end-of-travel zone, means for adjusting the slope and amplitude of the first signal to correspond to a predetermined speed curve and its predetermined slope for a normal slowdown at the end of the stroke, means giving a deflection signal whose amplitude corresponds to any deviation between the first and the second signal and a means giving a reference signal corresponding to the maximum permitted deviation and a comparison means for comparing the deflection signal and the reference signal and giving a predetermined signal when the actual speed deviation   exceeds the maximum permitted speed deviation.   Lifting system according to claim 1, comprising a means of modification implemented by the comparison means for modifying the operation of the   elevator system when the means of comparison nit the predetermined signal.   Lift system according to claim 1,   having means for blocking the first signal when   that it is reduced to a predetermined amplitude.   An elevator system according to claim 1 including means for providing signals indicating the direction of travel of the elevator car and the   presence of the elevator car in each terminal area   nal and means responding to the signals to give an authorization signal which authorizes the production of the signal   predetermined by the means of comparison only when   that the elevator car is getting closer to a level of   destination in an end-of-race area.   Elevator system according to claim 1, characterized in that the electromechanical transducer comprises a transformer having input and output windings and means for modifying the coupling between the input and output windings as a function of the position of the elevator car compared to the average marking.