Abstract: To achieve a particular price point and/or to utilize a particular engine, riding lawn mowers may be configured with reduced size, weight, and/or power requirements, in order. A riding lawn mower may comprise a cutting deck coupled to a cutting blade, and an internal combustion engine having a displacement of less than 225 cubic centimeters. The internal combustion engine may be coupled to the cutting blade via a friction drive, wherein the friction drive is configured with a neutral bearing in order to reduce flat spotting of components of the friction drive.

Abstract: Lawn mower and method for controlling self-driving operations of the lawn mower wherein the lawn mower and method include a mower body, multiple wheels for supporting the mower body, and a drive motor for driving at least one wheel. Also disclosed is a controlling method for the mower including the following steps: an operator inputs predetermined parameters via am input device, a processor controls an execution circuit to control the drive motor to work according to the predetermined parameters, a sensor checks the actual operating parameters of the drive motor and feeds them back to the processor, the processor compares the actual operating parameters with the predetermined parameters to produce control signals, the execution circuit receives and processes the control signals, and regulates the actual operating parameters of the drive motor according to the predetermined parameters. The method enables the operation convenient and comfortable.

Abstract: A trigger 52a control apparatus is provided for operating a transmission 44 of a self-propelled mowing machine 20 via a cable 42 between a halt condition and an advancement condition. The trigger 52a control apparatus includes a housing 100, and a plurality of independently operable triggers 52a rotatably coupled to the housing 100 for movement between an engaged and a disengaged position 104. Each trigger 52a includes an operation member 108a. A cam 114 is rotatably coupled to the housing 100 about a cam rotation axis 116 and operatively coupled to the cable 42, wherein rotation of the cam 114 in a first direction relatively increases tension in the cable 42. An actuation member 138 is coupled to the cam 114 a distance from the cam rotation axis 116.

Abstract: A return to neutral control mechanism for a zero turning radius mower is disclosed. The return to neutral control mechanism includes a pair of control levers pivotable between forward, neutral and reverse positions. A brake pedal is moveable between a disengaged position to an engaged position. In response to engagement of the brake pedal, a control pivot attached to each control lever moves each control lever to the neutral position. The return to neutral control mechanism may include a cam that rotates in response to engagement of the brake pedal, and a control pivot that follows the cam during engagement of the brake pedal.

Abstract: A baler (1) composed of a pick-up device (4) for picking up a crop string (12), a compression device for compressing the crop in a compression direction to form a bale, the compression device having components (19) for measuring a distribution of a charging degree transversely to the compression direction. The baler (1) also has a 3D imaging device (11) for recording a 3D image (23) of the field and the crop string (12) in front of the baler (1), and a control device including a data processor (13) for controlling the baler (1) in dependence on data from the 3D image (23) and the charging degree (25).

Abstract: A ground engaging work vehicle including a frame, a plurality of tractive elements, a movable extension, a hydraulic fluid using attachment, a hydraulic fluid pump and an accumulator. The plurality of tractive elements are coupled to the frame. The tractive elements engage the ground. The movable extension is connected to the frame. The hydraulic fluid using attachment is coupled to the movable extension. The hydraulic fluid pump is selectively fluidly coupled to the attachment. The accumulator is selectively fluidly coupled to the attachment dependent upon at least one fluid flow requirement of the attachment.

Abstract: An improved lawn mower having the ability to exhaust grass out of a left chute, a right chute, or a rear chute. The improved lawn mower of the present invention also having a belt system that has a reversing gear, enabling the belt system to travel in two opposite directions. The belt system driving a plurality of reversible, double-edged cutting blades having a fin that facilitates air flow in the direction of the cutting blade. The improved lawn mower also having a power coupling that can receive a lawn maintenance attachment.

Abstract: A gradual engagement system for use in power equipment is herein described. The gradual engagement system causes a clutch pulley to rotate around a clutch arm when an engagement tensile force is applied by an engagement spring. The engagement spring is attached to a pivot arm which is also connected to the clutch arm. The gradual engagement system allows the clutch arm to be pressed against a drive belt in a gradual fashion, providing for a smooth engagement of the various components of the power equipment.

Abstract: A self-propelled harvesting machine includes an internal combustion engine and an electronic control arrangement that is coupled to the internal combustion engine and that is provided as input the rotational speed of the internal combustion engine and that can be provided with information as to whether the harvesting machine is in operation on public roads or in a harvesting operation. The control arrangement provides as input during the harvesting operation in an automatic operating mode the rotational speed of the internal combustion engine as a function of the situation in a harvesting operation of the harvesting machine as controlled by the control arrangement. In addition, the internal combustion engine can be operated in an efficient operating mode at a local minimum of the specific fuel consumption.

Abstract: In a swather formed by a tractor and attached heeder for cutting standing crop to form a swath, reel speed and optionally draper speed are controlled relative to ground speed by a control system including a manually operable input and display available to the operator. The control system can be used in an automatic mode to set an index value for an actual difference in reel speed relative to ground speed and to vary reel speed accordingly. In this mode a manually operable control varies the index. The control system can be switched by the operator to manual in which case the same control varies the actual reel speed. Minimum reel speed can be set by the same control and when operative the automatic system does not allow reel speed to fall below the minimum set value despite the values of index and ground speed.

Abstract: Power equipment is designed to be operated by a user walking behind the power equipment, and includes an engine, a body, a drivetrain, a handle, a linkage, and a mechanism. The engine drives a working implement. The drivetrain links the engine to at least one wheel designed to drive the power equipment. The handle extends from the body, where at least a portion of the handle is designed to rotate relative to the body. Rotation of the at least a portion of the handle relative to the body is communicated to the drivetrain via the linkage, and controls a driving speed of the power equipment. The mechanism is designed to provide a mechanical advantage between rotation of the handle and operation of the linkage.

Abstract: Apparatuses and methods are provided for actuating a control component of a power machine. A two-step bail can be attached to a handle for controlling the power machine. The two-step bail can include a base member and a control member, wherein the control member can be slidably attached to the base member which can be pivotably mounted to the handle of the power machine. The control member can be depressed, by an operator first action, into the base member, which can be followed by an operator second action wherein the base member and control member can be pulled reward toward the operator to actuate a control component of the power machine.

Abstract: A trigger 52a control apparatus is provided for operating a transmission 44 of a self-propelled mowing machine 20 via a cable 42 between a halt condition and an advancement condition. The trigger 52a control apparatus includes a housing 100, and a plurality of independently operable triggers 52a rotatably coupled to the housing 100 for movement between an engaged and a disengaged position 104. Each trigger 52a includes an operation member 108a. A cam 114 is rotatably coupled to the housing 100 about a cam rotation axis 116 and operatively coupled to the cable 42, wherein rotation of the cam 114 in a first direction relatively increases tension in the cable 42. An actuation member 138 is coupled to the cam 114 a distance from the cam rotation axis 116.

Abstract: A variable speed control apparatus 240 is provided for controlling a self-propelled speed of a mowing machine 20 including an operational trigger 38 and a variable speed transmission 44. The variable speed control apparatus 240 includes a body 254 and a cable 242 coupled between the operational trigger 38 and the variable speed transmission 44, and a control lever 268 is rotatably coupled to the body 254 for rotational movement between a first position 70 and a second position 72. A cable tensioner 84 is operatively coupled to the control lever 268 and adapted to translate rotational motion of the control lever 268 to the cable coupler 86. Movement of the control lever 268 towards a first portion relatively decreases tension in the cable 242, and movement towards a second tensioner position relatively increases tension in the cable 242.

Abstract: A top adjusting linkage for leveling a mower deck includes a generally vertically aligned lift rod connecting a pair of pivotable arms supporting the mower deck. One of the lift arms may be pivotably connected to a deck lift pedal. The lift rod has an effective length between the pivotable arms, and an engageable upper end to change the effective length. A fender deck with an access hole is provided directly above the upper end of the lift rod, so that an operator can engage the upper end of the lift rod.

Abstract: A handle structure of a walk-behind working machine includes: a handle having left and right raised portions extending upward from a handle frame and a cross portion interconnecting the left and right raised portions; and a main clutch lever shiftable from a clutch-OFF position to a clutch-ON position by being pivoted into pressed abutment against the cross portion. The main clutch lever is constructed in such a manner that, when the main clutch lever is in abutment against the cross portion, a space for allowing a human operator to grip the left and right raised portions is secured between the left and right raised portions and the main clutch lever.

Abstract: An electric outdoor power machine includes a machine body supported by wheels and having an output member driven by a motor. The motor is powered by a source of electrical power such as a battery. An upright assembly extends from the machine body and has a gripping handle. A manual input member such as a bail handle is mounted adjacent to the gripping handle and is movable relative to the gripping handle between a deactivated position and an activated position. A control assembly that selectively communicates electric power to the output member includes a button supported by a housing on the upright assembly. The button is movable between an unactuated position and an actuated position. A button crank is coupled to the button and has an interface portion.

Abstract: The present subject matter discloses devices and methods for controlling the operation of a lawnmower or other walk-behind power machines without the use of a bail or operator presence control. A control device for a walk-behind machine can include a handle for a walk-behind machine, a sliding cam movable within the handle, a cable connected to the sliding cam and to a machine control component of the walk-behind machine, and an actuator movably attached to the handle. Movement of the actuator against a cam surface of the sliding cam can move the sliding cam within the handle to move the cable and operate the machine control component.

Abstract: A method for dividing a field into zones with similar crop attributes and developing a mission plan for steering the harvester to selectively harvest crops based on one or more of the attributes. The attributes include protein level, starch level, oil level, sugar content, moisture level, digestible nutrient level, or any other crop characteristic of interest. The method can be applied to selectively harvest and/or segregate according to attribute any crop, including grains such as wheat, corn, or beans, fruits such as grapes, and forage crops. Directed crop sampling provides absolute value and variance information for segregated batches of harvested crop.

Abstract: A walk behind lawn mower has an exit tunnel that is opened and closed by a pivotal mulch door to convert the mower between collecting and mulching modes of operation. An operating handle fixed to the mulch door includes a vertically reciprocal push button for releasing locking tabs that engage detents for holding the mulch door in the open and closed positions thereof. The bottom wall of the exit tunnel has a steeply inclined rear ramp section that is angled upwardly relative to the horizontal at least approximately 45°. The rear discharge opening of the exit tunnel occupies approximately an upper quarter of the area of the rear face of the cutting deck. Grass clippings flow into the upper portion of a grass collector through this high, steeply angled exit tunnel to promote even and full filling of the grass collector in the collecting mode.

Abstract: A control system for a BBC on a mower comprises a pivotal bail and a pivotal housing that is linked to the BBC. If a push member on the housing is pushed inwardly from the side of the housing before the bail is pivoted, then a pin moves to a blocking position behind the bail. Subsequent pivoting of the bail will pivot the housing to actuate the BBC. A channel in the housing frictionally grips the bail to prevent rebound of the bail when a spring force resets the housing and the bail to their initial positions after the operator releases the bail. Movement of the push member also closes an interlock switch which will kill operation of the engine if a grass discharge outlet on the mower is uncovered.

Abstract: Embodiments of the invention provide a control assembly and method of manufacturing a walk-behind mower having a transmission and an engine electrically connected to an operator presence switch. The control assembly can include a left drive lever and a right drive lever. The control assembly can also include a left control member and a right control member each coupled to the transmission. The control assembly can further include a left operator presence lever and a right operator presence lever coupled to the operator presence switch. The operator presence switch can allow the engine to operate when either the left operator presence lever is moved toward the left drive lever or the right operator presence lever is moved toward the right drive lever.

Abstract: Embodiments of the invention provide a control assembly and method of manufacturing a walk-behind mower having a transmission and an engine electrically connected to an operator presence switch. The control assembly can include a left drive lever and a right drive lever. The control assembly can also include a left control member and a right control member each coupled to the transmission. The control assembly can further include a left operator presence lever and a right operator presence lever coupled to the operator presence switch. The operator presence switch can allow the engine to operate when either the left operator presence lever is moved toward the left drive lever or the right operator presence lever is moved toward the right drive lever.

Abstract: This invention relates to a lawn mower. In certain example embodiments, the lawn mower may be of the walk-behind type. In certain example embodiments of this invention, the lawn mower may have one or more of: (a) an improved handlebar weldment assembly, (b) an improved operator presence control (OPC) system and structure, (c) an improved speed control system structure, (d) an improve cam bar system for hydraulic pump control, (e) a return-to-neutral biasing system that biases hand lever(s) toward a neutral position but only from a reverse position (not from a forward position), and/or (f) an improved tracking adjustment system.

Abstract: A method and apparatus for two motion cable engagement includes a housing adapted for attachment to a tubular member such as a handlebar or the like of a walk-behind lawnmower, a lever assembly pivotably mounted to the housing, and a socket operatively connectable to the lever assembly and actuatable by a deadman handle. The lever assembly preferably includes a lever, a hub connected to the lever, and a pivotable member which is selectively pivotably driven by the hub. When the socket is pivoted by the deadman handle from a primary position to an engaged position, movement of the lever from an initial position to an advanced position produces pivoting of the pivotable member and a control cable attached thereto.

Abstract: A control system for use with a ground maintenance vehicle such as a lawn mower. The control system may include one or more control handles movable between a neutral position and at least a first drive or reverse position. The system may further include a biasing mechanism operable to bias the control handle from the first drive position to the neutral position. The biasing mechanism may be pre-deflected when the control handle is in the neutral position, yet provide little or no biasing effect to the handle until the handle is moved towards the first drive position.

Abstract: With a rotary mower having a driveline including a plurality of gearboxes, a method of operating the rotary mower includes providing a sensor operative to measure a temperature of each gearbox in the driveline; monitoring the temperature in each gear box; and operating the mower to maintain the temperature of each gearbox at a level below a maximum acceptable temperature.

Abstract: A hand grip with half-shells is constructed so as to be able to be fastened to a tubular pipe, and is provided with a mounting opening for the tubular pipe which on the one hand is securely fastened to the tube and on the other hand does not have any intrusive bores in the grip region, in which there is to be a generous space available for a grip mechanism. Each half-shell is provided with a holding arrangement corresponding to the tubular pipe, so that the two holding arrangements form a form-fitting mounting for the respective half-shell on the tubular pipe.

Abstract: Apparatuses and methods are provided for controlling a self-propelled machine, such as a lawn mowing machine, including a housing, a handle attached to the housing, and a prime mover attached to the housing with a variable speed transmission for propelling the mowing machine. A variable speed adjustable twist control is provided and can include an elongate body moveable in a twisting manner and an adjustable bracket lockably adapted to the elongate body for twisting with the elongate body and the adjustable bracket having an inner channel adapted for guiding a cable control connector operatively connected to the variable speed transmission through a cable for controlling the variable speed transmission, whereby self-propelled speed of the mowing machine can be controlled by operating the adjustable twist control.

Abstract: A ground speed control system for an outdoor power equipment unit comprises a slidable handle grip that moves up and down on a handle to decrease and increase the ground speed, respectively. A pivotal control lever is provided on the handle grip. The pivotal lever includes a toothed sector gear. A toothed rack is fixed to the handle. Normally, the sector gear and toothed rack are out of engagement with each other during sliding motion of the handle grip. However, if the operator pivots the control lever to engage the sector gear with the rack, cooperation between the teeth of the sector gear and the teeth of the rack will move the slidable handle grip further down the handle to provide a temporary speed increase and will also lock the handle grip to the handle to provide cruise control capability. The handle grip is U-shaped and has two legs telescopically received inside the open upper ends of a pair of spaced handle tubes.

Abstract: A non-contact neutral sensing apparatus with directional feedback in a vehicle directional control system for an agricultural or construction vehicle.

Abstract: A handle structure of a walk-behind working machine includes: a handle having left and right raised portions extending upward from a handle frame and a cross portion interconnecting the left and right raised portions; and a main clutch lever shiftable from a clutch-OFF position to a clutch-ON position by being pivoted into pressed abutment against the cross portion. The main clutch lever is constructed in such a manner that, when the main clutch lever is in abutment against the cross portion, a space for allowing a human operator to grip the left and right raised portions is secured between the left and right raised portions and the main clutch lever.

Abstract: Apparatuses and methods are provided for controlling a self-propelled machine, such as a lawn mowing machine, including a housing, a handle attached to the housing, and a prime mover attached to the housing with a variable speed transmission for propelling the mowing machine. A variable speed adjustable twist control is provided and can include an elongate body moveable in a twisting manner and an adjustable bracket lockably adapted to the elongate body for twisting with the elongate body and the adjustable bracket having an inner channel adapted for guiding a cable control connector operatively connected to the variable speed transmission through a cable for controlling the variable speed transmission, whereby self-propelled speed of the mowing machine can be controlled by operating the adjustable twist control.

Abstract: A walk-behind lawn mower includes at least one of: (a) a latch assembly for receiving a folded-up sulky for storage during transport and the like; (b) inboard mounted control rods extending downwardly from a handle control assembly area of the mower, so that actuator shafts for the hydraulic pumps are located on inboard sides of the pumps so as to oppose one another; (c) a handle control assembly for allowing the mower to be operated in an efficient manner with operator comfort during turns and the like; and/or (d) a pump lock-out system including a lever(s) for actuating both a braking force to be applied to at least one wheel of the mower and a pump lock-out system for causing the pumps to be locked in a neutral position.

Abstract: Apparatuses are provided for controlling a self-propelled machine wherein the apparatuses include a handle and a control device and can utilize first and second linking members. The control device is pivotably coupled to the handle, and includes a slidable control portion that is linearly translatable relative to the handle. The first linking member includes a first proximal section that is coupled to the control device, and a first distal section that is engagable with the machine. The first linking member is actuatable in response to pivoting of the control device. The second linking member includes a second proximal section coupled to the control device and a first distal section engagable with a transmission. The second linking member is actuatable in response to sliding of the slidable control portion. The control device can be pivoted between an ON state and an OFF state to implement operator presence control. The slidable control portion can be linearly translated to implement variable speed control.

Abstract: Apparatuses and methods are provided for actuating a control component of a power machine. A two-step bail can be attached to a handle for controlling the power machine. The two-step bail can include a base member and a control member, wherein the control member can be slidably attached to the base member which can be pivotably mounted to the handle of the power machine. The control member can be depressed, by an operator first action, into the base member, which can be followed by an operator second action wherein the base member and control member can be pulled reward toward the operator to actuate a control component of the power machine.

Abstract: Self-propelled work vehicle for harvesting fruit, with a front axle, a rear axle, a steering column, an engine, a control pedal, a seat mounted in a driving position and a plurality of tools, with a control system for controlling the engine, the tools, the control pedal. The control system comprises an electronic joystick, which controls the progress of the self-propelled work vehicle for harvesting fruit so that acceleration and braking are proportional with respect to the angle is maintained when the electronic joystick is released.

Abstract: A hybrid electric lawnmower is described which includes an electric motor operating the blade and the ability to drive the motor from either 120 VAC line voltage or from a battery pack. There is a user selectable power selection switch for switching between DC or AC power and also a boost and conserve feature which allows for increased speed of the blade as necessary. Running the mower at the conserve setting prolongs battery pack duration per charge.

Abstract: This invention relates to a lawn mower. In certain example embodiments, the lawn mower includes one or more of: (a) a cooling baffle for efficiently cooling a hydraulic fluid tank and/or fluid therein using air flow caused by a combustion engine used for driving mower cutting blade(s); (b) improved cockpit structure including fenders; (c) improved drive wheel(s) adjustment structure or assembly; (d) improved idler arm assembly for use in connection with the cutter deck and/or pump driving belt; and/or (e) improved hose routing structure.

Abstract: A dual lever steering control mechanism for a mounting a control lever or stick to a mower is disclosed. The mechanism includes a housing with an opening, a forward/reverse lever insertable through the opening and pivoting on a first axis, and a neutral position lever pivotably attached to the forward/reverse lever to pivot on a second axis transverse to the first axis. The control lever may be attached to the neutral position lever at a plurality of different height and fore/aft settings.

Abstract: A riding lawnmower vehicle includes two main drive wheels, at least one caster wheel, an electric traction motor, an internal combustion engine, a generator driven by the internal combustion engine, and a lawnmower. The electric energy generated by the generator can be supplied directly or via an electric accumulator to the electric traction motor. The main drive wheels are independently driven by the electric traction motor, which can operate as a traction power source. When viewed from one end to the other end in the width direction of the vehicle, the internal combustion engine and a secondary battery operable as the electric accumulator overlap each other, and the main drive wheels overlap at least a part of at least one of the internal combustion engine, the generator, the secondary battery, a fuel cell, a capacitor, an inverter, a cooling device, a mower driving motor, and a grass-collecting duct.

Abstract: An automatic coupling and latching assembly, for coupling a combine feeder and a combine header from the cab of a combine harvester, said assembly comprising a stationary gearbox with a telescopic jackshaft assembly extending therefrom, a shift fork activation unit, and comprising spring loaded retainers, is disclosed.

Abstract: A dual lever steering control mechanism for a zero turning radius mower includes left and right steering levers that are independently pivotable fore and aft between reverse, neutral and forward positions. Steering lever grips are attached to and project from the steering levers. Each steering lever grip has a mounting surface with an electrical switch on the mounting surface, and a protective structure extending from the mounting surface.

Abstract: A riding mower assembly may include a mower frame, first and second wheels, and a steering assembly. The steering assembly may include a steering frame member fixed to the mower frame, a first steering arm rotatably coupled to a first end of the steering frame member and having the first wheel coupled thereto, a second steering arm rotatably coupled to a second end of the steering frame member and having the second wheel coupled thereto, an actuation mechanism, and a cross-member. The actuation mechanism may include a first end coupled to the steering frame member and a second end coupled to the first steering arm. The actuation mechanism may include a motor having an actuation arm extending therefrom that rotates the first steering arm. The cross-member may have a first end coupled to the first steering arm and a second end coupled to the second steering arm.

Abstract: The present invention provides a control adapter for use with an existing dual lever lawn tractor that allows an operator to use a single hand in operating tile dual lever lawn tractor. Existing dual lever lawn tractors require an operator to use one hand on each lever to operate the lawn tractor. The control adapter of the present invention is operatively connected to the first control lever and to the second control lever of the dual lever lawn tractor which allows the operator to use a single hand in operating the dual lever lawn tractor.

Abstract: In a lawnmower engine speed control system having an actuator moving a throttle valve and a controller controlling operation of the actuator such that the engine speed becomes equal to a predefined desired engine speed, it is determined whether the lawnmower is under a mowing operation based on a value indicative of a load of the engine including an operation rate or output of the engine, the desired engine speed is changed based on a result of determination, thereby enabling to lower noise, to boost fuel efficiency, and to simplify operation by making manual regulation of engine speed unnecessary, while ensuring stable operation free from engine speed variance.

Abstract: A tractor has hydraulically driven wheels at a cab end and castor wheels at an engine end. It can be driven cab forward in a working mode with a header on the forward end. It is rotated to engine forward in the transport position for more stable higher speed travel. The driver's console is rotated in the cab with the steering and speed control elements moved with the seat for the driver to face forwards and its position is detected by switches. In the engine forward position for transportation, the control system detects the seat position and operates the controls for higher speed drive and to prevent operation of the header. The engine has a series of ratings which can be selected depending upon whether the header motor is engaged so that a highest engine speed is used only when the header is disengaged and the lower speed is used for higher fuel efficiency when the header is operating.

Abstract: A mower has at least one powered cutting unit for mowing grass. A switch is provided for permitting operation of the cutting unit or for preventing operation of the cutting unit depending upon the state of the switch. The switch is linked in some fashion, e.g. mechanically or electronically, to the traction drive system of the unit. The ground speed of the mower is limited to a mowing speed when the switch is placed into the state in which operation of the cutting unit is permitted. When the switch is placed into the state in which operation of the cutting unit is prevented, the ground speed of the mower is not limited to the mowing speed but can attain a higher transport speed.

Abstract: Apparatuses and methods are provided for controlling a self-propelled machine, such as a lawn mowing machine, including a housing, a handle attached to the housing, and a prime mover attached to the housing with a variable speed transmission for propelling the mowing machine. A variable speed twist control is provided including an elongate body moveable in a twisting manner, the body having an inner channel adapted for guiding a cable control connector operatively connected to the variable speed transmission through a cable for controlling the variable speed transmission, whereby self-propelled speed of the mowing machine can be controlled by operating the twist control.

Abstract: Apparatuses and methods are provided for controlling a self-propelled machine wherein the apparatuses and methods include a handle and a control device and can utilize first and second linking members. The control device is pivotably coupled to the handle, and includes a slidable control portion that is linearly translatable relative to the handle. The first linking member includes a first proximal section that is coupled to the control device, and a first distal section that is engagable with the machine. The first linking member is actuatable in response to pivoting of the control device. The second linking member includes a second proximal section coupled to the control device and a first distal section engagable with a transmission. The second linking member is actuatable in response to sliding of the slidable control portion. The control device can be pivoted between an ON state and an OFF state to implement operator presence control.