fig1 shows the schematic circuit arrangement of a circuit for controlling a height - adjustable table , wherein it can be seen in the illustration that the force - sensitive sensor and the measuring resistance are connected in series . the electrical resistance of the measuring resistance is fixed , therefore it does not vary . the electrical resistance of the force - sensitive sensor becomes less in the case of an application of force onto the sensor or respectively increases in a case in which the application of force onto the sensor decreases . a supply voltage is applied over the series connection , consisting of the force - sensitive sensor and the measuring resistance , wherein the lower end of the measuring resistance is connected to earth . between measuring resistance and force - sensitive sensor a node point is formed , as can be seen in fig1 . at this node , a filter can be connected . the filter is provided to filter the chronological course of the voltage drop over the measuring resistance , i . e . to remove interferences and irrelevant deflections therefrom . at the output of the filter , which can be seen on the right - hand side of the filter in fig1 , a microcontroller is connected . between earth and filter output , the interference - suppressed voltage can now be measured , which drops over the measuring resistance . as the circuit of measuring resistance and force - sensitive sensor is a series connection , and the supply voltage is applied over the entire series connection , the overall resistance of the series connection is composed of the added resistances of the force - sensitive sensor and of the measuring resistance . this means that the voltage likewise varies over the measuring resistance which can be measured at the filter output , with a variation of the electrical resistance of the force - sensitive sensor . this means that via a measurement of the voltage drop over the measuring resistance indirectly also the application of force of a physical force onto the force - sensitive sensor can be measured . the interference - suppressed voltage of the measuring resistance is now emitted at the filter and serves as input voltage for the microcontroller . the latter has as first component an analog - digital converter , which converts the analog input voltage of the measuring resistance into a digital signal . this digital signal can now be processed by a processing unit . this processing unit can generate output signals which can be emitted via an output unit to , for example , an electric motor for the height adjustment of a table . as can be seen in fig1 , in this embodiment the components analog - digital converter , processing unit and output unit are integrated into the microcontroller . however , this is not imperatively necessary . fig2 shows a schematic flow diagram for signal processing for the control of the height - adjustable table according to the invention , with a column or respectively with a sensor . the absolute force measured by the force - sensitive sensor is designated as f . in the state of rest of the table , f = f 0 , wherein f 0 represents the basic load which is measured by the force - sensitive sensor in the state of rest of the table , without the latter being controlled for raising or respectively lowering . the described sequence begins in the “ start ” field , the first step consists in the interrogation of the sensor . in this sensor interrogation , the currently measured force f , which is measured by the force - sensitive sensor , is interrogated . in the same step , a decision is made as to whether a force difference δf is present , wherein δf = f = f 0 applies , and this force difference δf is greater than a force difference δf wake - up , wherein the force difference δf wake - up represents a force difference which is necessary for the waking up of the table control . this therefore concerns a force impulse which must be applied by a user onto the table plate in order to inform the control that a movement is desired . the user thereby wakes the control up from its state of rest and sets it into an active state . in the step “ interrogation sensor rest ”, it is therefore determined whether δf & gt ; δf wake - up . the above - mentioned embodiments with regard to the wake - up signal are only to be understood as being by way of example and for the sake of simplicity are only defined with a force impulse . in practice , it will be necessary to define a more individual signal or respectively a signal sequence as wake - up signal , so that malfunctions can not arise inadvertently . for example , a shaking or an upward pulling or pressing downward carried out briefly twice in succession could be defined as wake - up signal . this predefined wake - up signal must then be stored in the control . if the interrogation produces “ no ”, the sequence continues to a second time emitter , which now delays the sequence until a previously determined time span δt 2 has elapsed . the time span δt 2 can lie for example at 100 ms . thereafter , the sequence continues to the step “ interrogation sensor rest ”. if , in the step “ interrogation sensor rest ”, the condition δf & gt ; δf wake - up is present , the control continues to the step “ control wakes up ”. here , it is , furthermore , expedient for the fulfilling of this condition , that the application of force must have disappeared again after a short time , in order to be able to differentiate a pressing down of the table plate from the placing of an object on the table plate . on fulfilling of the condition of the step “ interrogation sensor rest ”, the state of rest of the control is subsequently relinquished , it is now connected actively . the sequence now continues to the step “ interrogation sensor active ”. in this step , a check is made as to whether the signal is δf & gt ; 0 . if yes , the sequence continues to the step “ control decides whether start - up criterion is fulfilled ”. in this step , the control decides whether δf & gt ; δf min , wherein δf min represents precisely the application of force which must be expended by a user onto the table plate in order to trigger a movement of the table plate . if the condition δf & gt ; δf min is not fulfilled , the sequence continues to the step “ time emitter 1 ”. as long as a predetermined time span δt 1 has not elapsed , it is now determined permanently in the step “ interrogation sensor active ” whether δf & gt ; 0 . if δf & gt ; 0 , the sequence continues to the step “ control decides whether start - up criterion is fulfilled ” and the first time emitter loses its effect . if , however , the condition δf & gt ; 0 is not present for a period of time δt 1 , the sequence continues to the step “ control falls asleep ”. the period of time δt 1 can lie in a range from a few seconds to several minutes . when , in the step “ control decides whether start - up criterion is fulfilled ”, it is determined that δf & gt ; δf min , this means that the control has recognized that a user wishes to move the height of a table plate . now a check is made in step “ decision jamming event ” as to whether the signal δf remains largely constant , or whether this changes intensively . if the signal δf remains constant , the motor is moved as long as the condition δf & gt ; δf min applies . thereafter , the moving of the motor is terminated , and the sequence returns to the step “ interrogation sensor active ”. if in the step “ decision jamming event ” it is determined that the signal af changes intensively , a collision of the moved table plate with an object is determined , and the sequence continues to the step “ stop motor ”, in which the moving of the table plate is terminated . thereafter , the sequence continues to step “ time emitter 1 ”. as long as a predetermined time span δt 1 has not elapsed , it is now permanently determined in the step “ interrogation sensor active ” whether δf & gt ; 0 . if this condition is present , the first time emitter loses its effect again and the sequence continues to the step “ control decides whether start - up criterion is fulfilled ”. and if the condition δf & gt ; 0 is not present for a time period δt 1 , the sequence again continues to the step “ control falls asleep ”. it is , in addition , expedient , that the application of force δf between the step “ control wakes up ” and “ interrogation sensor active ” or “ interrogation sensor rest ” and “ control wakes up ” must be zero for a time period of for example 1 to 2 seconds . otherwise , for example , an adjustment of a table plate could be triggered by two weights placed in succession on a table plate . the described circuit and the described method could also be modified to the effect that instead of the force - sensitive sensor a strain gauge ( dms sensor ), a pressure sensor , or else a piezo element is used in order to detect an application of force onto a movable part of a table . in addition , also several identical or different sensors could be used . irrespective of the sensor used for this , this waking up could , in addition , take place not only by a pressing down or respectively pulling up of a movable part of a table , but also by a lateral wobbling or shaking on , for example , a table plate . generally , all statements which are directed to a height - adjustable table also apply to all other types of height - adjustable pieces of furniture . in the case of a table according to a second embodiment with two columns , the control takes place as follows . a sensor is associated with each column . a sensor control is provided . the control unit has a storage unit in which , inter alia , a predetermined wake - up signal is stored , which is compared with the signals of the sensors in order to be able to determine a wake - up function . in the present example , the wake - up signal exists , which is emitted from a pulling up twice of the table plate within a time span of two seconds by the sensors . in order to detect which sensor signal is to be taken into consideration , and which is to be ignored , a comparison unit is provided , which compares the loads of the two sensors with one another . a determination unit then determines as master sensor the sensor which experiences the greater application of force . when the wake - up function has been determined , the subsequent signal of the sensor is used as command , so that the control unit moves the table plate upwards or downwards , as long as the master sensor determines a continuous load upwards or respectively downwards . according to a particular embodiment , it is possible to take into consideration the extent of the force which is exerted onto the force sensor by pressing onto , or respectively pulling of , the table plate or respectively of the height - adjustable furniture part , so that through stronger pressing or respectively pulling the adjustment speed increases accordingly . with little force , the adjustment speed will decrease accordingly . thereby , the operability and the ease of use increases considerably . the control unit is adapted to cease with the moving of the table plate as soon as the continuous load ceases . this takes place either by letting go of the table plate or by colliding against an obstacle or an end switch , because thereby the signal indeed does not cease , but rather either becomes oppositely directed , because the run - up against an obstacle or against an end switch generates a contrary counterforce , or increases up to over a threshold value which is to be established in advance , from which it follows that the risk of damage or of injury to the operating personnel is present . when the lifting column must be calibrated in its position , i . e . when the lifting column must ascertain its current position , it is usual to carry out a reset function for the calibration of the position of the lifting column . for this , a switch is used , which is actuated for switching the carrying out of the reset function . it is advantageous , instead of the switch for switching the carrying out of the reset function , to deposit in the control a previously established sensor signal course for carrying out a reset , which differs from the wake - up signal . by recognizing the sensor signal course for carrying out a reset in the case of corresponding pulling up or respectively pressing down or shaking of the lifting column , as is delivered from the sensor to the control , the control determines that the reset function is to be carried out . in addition , it is advantageous that the table plate can be operated from all sides . this represents in particular a great advantage compared with conventional solutions , in which a membrane switch or an induction loop has to be provided on the table plate at the locations at which the operation is to take place . in addition , it is advantageous , alongside the sensor ( s ) for the input of control commands to provide at least one additional sensor , which serves as sensor for a jam protection mechanism . the sensor for the input of control commands and the sensor of the jam protection mechanism can be arranged one over another here . this arrangement can , in addition , be arranged or respectively accommodated inside the height adjustment device . with the use of additional sensors for the detection of collisions ( jamming ), it is , in addition , advantageous that the sensors have different sensitivities for signal detection . the sensitivity of the sensor for the detection of control commands can be higher here ( therefore more sensitive ) than the sensitivity of the sensor for the detection of collisions . this is because with the executing of control signals onto a table plate , smaller forces will occur than in the case of a collision or respectively of a jam . the sensitivities of the sensors are optimized here for their field of application . in addition , the control is advantageously adapted to carry out a learning mode or respectively to change into the latter . in this learning mode , all commands , by which for example a height - adjustable table can be operated by a user , can be individually determined and programmed in . on an activation of the learning mode , a user can , for example , input the command , by which the control is woken up and changes into an operating mode . for this , the control detects the command “ played ” by the user , or respectively the course of the sensor values resulting therefrom . the control processes and modifies the signal ( the course ) thereupon , in order to subsequently store the command of the user . such a “ teaching ” of new commands is conceivable for each function of the height - adjustable table . finally , it is also to be noted that all the embodiments which refer to a height - adjustable table are likewise transferrable to all height - adjustable items of furniture and likewise to beds , in particular hospital beds . the previously described embodiments are therefore also to be transferrable and likewise apply to these additional possibilities of application .
a circuit controls a height - adjustable table . a current load acts on the table plate and is measured by a force - sensitive sensor and serves as control signal of a control according to the invention . derived from this signal , a collision of the electrically height - adjustable table with fixed objects is recognized . control signals are also detected , which are inputted by an operator of the table in the form of applications of force onto the table plate . here the table or respectively the control device is situated in a state of rest until the user of the table exerts a brief force impulse onto the table plate , i . e . presses once onto the table plate . thereafter , the control changes from a state of rest into an operating state and waits for control inputs . when the user now presses from above onto the table plate , the latter moves electrically downwards .