DE102008005837A1 - Security device and system - Google Patents

Abstract

The device (1) has a controlling and evaluation unit (2) designed for outputting switching signals to a safety-adjusted output (OSSD-LG1), where the output is provided for switching an actuator. The controlling and evaluation unit comprises a back-read unit (OSSD-MON1) to backread the switching signals at the output. The controlling and evaluation unit is designed to read and/or output control information at a control line (TOKEN). A switching unit (CTRL1) is designed for switching an object detection signal.

Description

The The invention relates to a safety device according to the preamble of claim 1.

such Safety devices are used for safe switching off of electrical loads, in particular an electrically driven Machine to avoid dangerous situations in particular and switch off the machine beforehand if necessary. The danger Situations brought by appropriate sensors or Switch monitors and detects and on with the sensors forwarded connected switching devices. With the term Safety device should also be such secure sensors, Safety switching devices or safety controllers understood become.

Such safety devices in the sense of this application are preferably designed as safe devices, sensors, safety switching devices or safety controls in the sense of machine safety, which means that these devices or the evaluation and / or control units connected to them comply with the relevant standards EN 954 which prescribes a classification into safety categories, for example category 2 to 4, or after EN 61508 , which prescribes safety levels, for example SIL 1 to SIL 3, or other safety standards. For example, these standards and regulations prescribe certain security against tampering and fail-safety.

From the EP 1 493 064 B1 and the EP 1 262 021 B1 Devices are known for fail-safe switching off electrical loads, especially in industrial production plants, with a first and at least a second safety switching device, the safety switching devices are connected in series and the output of the first switching device is connected to an input of the second switching device. The disadvantage here is the provision of additional inputs and a control and evaluation unit per safety switching device for processing the incoming signals.

It Object of the present invention, an improved safety device provide.

The The object is achieved according to claim 1 with a safety device with a control and evaluation unit and at least one safety-related output for switching an actuator, wherein the control and evaluation unit is formed is to output switching signals on the safety-related output. The control and evaluation unit has a read-back unit to read back switching signals on the safety-related output.

The Task is further solved by a system with at least Two safety devices for generating safety-related Signals. The security devices are over theirs Safety-related outputs can be connected to one another.

Thereby can be outputs of safety devices be connected directly to each other. The safety-related Outputs are similar to a bus system grouped together on a common line leading to the control a common actuator is used. It is an, or 'link the safety-related outputs of the safety devices. Once one of the devices a switching signal for shutdown sends a dangerous movement, this signal is sent to the Actuator passed on. By linking the safety-related Outputs on a common line decreases the Wiring effort between the safety devices considerably. Thus, only one single line has to be routed to an actuator become. By the, or 'combination of the safety-related Outputs also shorten a response time considerably, since every safety-related output is directly connected affects the actuator.

In order to each safety device the current signal state of the Safety-related output detects is in the control and Evaluation unit provided a read-back unit, which is formed, the switching state of the safety-related output read back. This ensures that a Switching signal issued by another safety device is not unduly changed, so for example safely prevents an object detection signal by a free signal is overwritten.

Advantageous If the control and evaluation unit is designed, control information to read and / or output on a control line. The control line is intended to provide information to a second security device pass. This can be a time-dependent sequence the security devices are provided, as in a time slot method, to the signal states on the safety-related output issue. For this purpose, with the help of the control line signals, for example a token, ie a bit pattern for the timing of the safety devices replaced. One of the safety devices takes over a master or host function, if this security device owns the token. The other security devices take over a slave or guest function.

However, it can also be provided that the safety devices simultaneously perform their safety function and at the same time output signals to the safety-related outputs. Then On the control line, information regarding coordination of the signal output on the safety-related outputs is exchanged. This makes it possible for the other safety devices to adapt their signals to the already existing signals of the safety-related outputs. Thus, it is inventively to avoid unnecessarily opposite signal levels are switched by different security devices, otherwise unnecessary currents flow on the common output line between the security devices.

Of the Safety-related output is designed to be at least two Switching signals, namely an object detection signal and to output a release signal. In a special state of the safety-related output are switched potential-free. The Switching signal object detection signal is output when a Event has been detected and a dangerous movement off is. Conversely, the free signal is output if no event was determined and a dangerous movement was not stopped shall be. In addition, the state is provided, wherein the safety-related output is potential-free. this is the Case, if the safety device is inactive and no protective field or event evaluation. This is necessary, for example, if the security devices for certain times do not carry out a safety check should, therefore, are inactive, since the security device, for example in a time slot method with a second security device works and the security devices at the same time Activation would interfere with each other.

In a preferred embodiment, the safety-related output has a switching voltage of 0 V to 3.5 volts when an object detection signal is applied, and a switching voltage of 24 volts with a tolerance of + -2.5 volts when a release signal is output a switching current of 0 to 600 mA. This makes it possible to control relays or contactors directly with the safety-related output. Several safety devices can thus act on a single relay to switch off a dangerous movement. However, the intended switching levels are also suitable inputs according to the standard EN / IEC61131 to switch. Programmable logic controllers have, for example, such inputs.

In Further development of the invention is the release signal of a first or second safety-related output by the object detection signal a second or first safety-related output overwritable. So it is provided, if by all safety devices a release signal is output, ie a level of 24 V is applied, that this signal by an object detection signal with the level 0 V is overwritten. This may cause the resulting common safety-related output with the shutdown a dangerous movement directly applied signal necessary without noticing the signals of the other safety devices or to consider. this leads to for a quick and immediate shutdown. Vice versa but it is not intended that an object detection signal is overwritten by a release signal. This even needs be prevented according to the present invention, as this causes a dangerous condition can be.

In Further development of the invention comprises the control and evaluation unit a semiconductor circuit having at least two switching units, wherein a first switching unit for switching the object detection signal is formed and a second switching unit for switching the release signal is trained. Is the first switching unit operated and the second switching unit is not actuated, so is the safety-related output to an object detection signal. However, if the first switching unit is not actuated and the actuated second switching unit, so there is a release signal at. If none of the switching units is actuated, then there is no Signal on the safety-related switching output, so that this is potential-free. If both switching units are switched simultaneously, for safety, an object detection signal is output, However, this case should be avoided, as this makes it unnecessary Electricity flows between the two switching units.

In Another embodiment is the control and evaluation unit two-channel executed. The control and evaluation unit can be redundant and / or diversified be. The dual-channeling ensures that occurring Single error does not cause a malfunction within the control and evaluate unit. Rather, occurring Single error detected and it can not cause an error and thus come to an uncertain state.

According to the invention the control and evaluation designed to the safety-related Output to test pulses to test. By the test pulses are The signals of the safety-related output briefly repeated on switched an opposite voltage level to check whether a switch to the opposite level possible would. The test pulses are so short that a connected Actuator or a connected signal processing device due to its inertia not through the test pulses on. The test pulses have a pulse duration of 100 μ bis 400 μs and the test pulses occur two to ten times per Second up.

According to the Invention are the test pulses by the control and evaluation output from the security devices. In doing so, every security device For example, check alternately whether the common safety-related Output would be switchable to an object detection signal. Either the master / host working in the Ownership of the token is and periodically passes the token to the slave / guest then test their circuit or test the slave / guest their first switching unit parallel to the master / host. For synchronization the processes between the safety devices become the test pulses from the respective evaluation evaluated accordingly.

In Further development of the invention are the security devices Safety relays or safety controllers. Thereby is it possible to use safety relays and safety controllers with the safety-related outputs to each other connect, for switching a common actuator.

In a particular embodiment, the security devices optical sensors, in particular light barriers or light grids. This makes it possible to use the safety-related outputs from sensors directly to each other. For example the access area to a robot cell of several safety sensors secured, so each object detection signal of the respective sensor to a shutdown of the robot cell. It can the photocells or light grids for generating large Protective fields or of protective fields in several levels next to each other become. The safety-related outputs of the individual Light grids are now linked according to the invention, to issue a common shutdown signal. So that the light grid is not interfere with each other, activate the light grid in Vote to each other. It is also planned to use sensors, Safety relays or safety controllers via to connect the safety-related outputs with each other, to control a common actuator.

in the The invention is based on exemplary embodiments explained in detail with reference to the drawing.

In the drawing shows:

1 a schematic representation of two light grids connected to each other;

2 a timing diagram for the signal sequences of a safety-related output.

1 shows two security devices 1 , in this embodiment, two light grids LG1 and LG2, which are arranged side by side. Light grids LG1 and LG2 are used to protect people from dangerous movements. Between a transmitter and a receiver of a light grid LG1 and LG2, a protective field is formed, upon the violation of which an intervention signal outputs a switch-off signal on a safety-related output OSSD_LG1 or OSSD_LG2. In order to fully secure a danger area, it is usually necessary to connect several light grids LG1 and LG2 with each other in order to extend a protective field or to provide protective fields at different positions. For this purpose, the safety-related outputs OSSD_LG1 and OSSD_LG2 of the individual light grids LG1 and LG2 must be linked to one another. According to the invention this linkage is performed without additional wiring. For this purpose, the safety-related outputs OSSD_LG1 and OSSD_LG2 of the individual light grids LG1 and LG2 are simply electrically connected to a common safety-related output OSSD for controlling a relay / contactor or for controlling an actuator, relay or contactor.

The Abbreviation OSSD stands for Output Signal Switching Device and names the part of a non-contact Protective device, in this case the light grid LG1 or LG2, which is connected to a machine control and in one Shutdown state transitions when the light curtain LG1 or LG2 detects an object. The light curtains LG1 and LG2 are over a common power supply connected. The power supply indicates the signals Function ground FE, 24 V, and, Ground` GND or 0V on.

Within the light grids LG1 and LG2, the safety-related output OSSD_LG1 and OSSD_LG2, each with two switching units CTRH1 and CTRL1 or CTRH2 and CTRL2 of a semiconductor circuit 6 respectively. 6 ' connected. A first switching unit CTRH1 allows the safety-related output OSSD_LG1 to be connected to 24 V and thus to output a free signal. The safety-related output OSSD_LG1 is connected to the second switching unit CTRL1, whereby the safety-related output OSSD_LG1 can be acted upon by 0 V. This corresponds to the output of an object detection signal. If both switching units CTRH1 and CTRL1 are open, there is no signal on the safety-related output OSSD_LG1 and thus a potential-free state. The signal on a common safety-related output OSSD can thus be influenced by both light curtains.

If the safety-related output OSSD_LG1 still has an object detection signal, ver caused by the light grid LG1 have, so this condition can be reset for safety reasons only by the same light grid LG1 with the release signal. This is necessary because only the device which generated the object detection signal can also cancel this to ensure that a detected dangerous condition is canceled.

Furthermore, the safety-related output OSSD_LG1 is connected to a read-back unit OSSD_MON1, whereby the control and evaluation unit 2 of the light grid LG1 is able to read back and check the respective signal of the safety-related output OSSD_LG1. For example, it is possible to check via the read back unit OSSD_MON1 whether an object detection signal or a free signal is applied to the safety-related output OSSD_LG1.

The Light grid LG1 has a control input TOKEN_IN and a Control output TOKEN_OUT on. The control output TOKEN_OUT of the first Light grid LG1 is connected to the control input TOKEN_IN of the second Light grid LG2 connected. However, it is also provided on a control line TOKEN both control signals as well as read, so to provide a bidirectional connection. That would the control input TOKEN_IN and the control output TOKEN_OUT a form common connection.

In a first exemplary embodiment, it is provided that the light grids LG1 and LG2 mutually execute their light grating functions. As a result, the light grids LG1 and LG2 can not influence each other visually. The light grid LG1 and the light grid LG2 thus work alternately successively in a so-called time slot method. The light grid LG1 checks its protective field status and outputs the free signal to the safety-related output OSSD_LG1 if the protective field is not damaged. At this time, no signal is output from the light grid LG2 on the safety-related output OSSD_LG2, ie a potential-free state, thus the output signal of the light grid LG1 is the decisive one. At the safety-related output OSSD is thus a signal of 24 V at. When the LG1 light curtain has finished evaluating its protective field, it is sent via the control line 8th told the LG2 light grid that the LG2 light grid can start evaluating its protective field. For this purpose, the light grid LG2 first reads the signal state of the safety-related output OSSD via the read-back unit OSSD_MON2.

Lies but a free signal on the safety-related output OSSD On, the light grid LG2 can after evaluation of its protective field the result of protective field evaluation on the safety-related Output OSSD_LG2 output. Is the protective field of the light grid LG2 is injured by an object, so is now from the light grid LG2 the object detection signal on the safety-related Output OSSD_LG2 output. This is the unit via the Schaltein CTRL2 of the light grid LG2 the object detection signal on the Safety-related output OSSD_LG2 switched. In case that If no object has been detected, the free signal on the safety-related Output OSSD_LG2 output. This is done by the internal switching unit CTRH2 the signal level of 24 V to the safety-related output OSSD_LG2 switched.

In A second embodiment is now intended that the light grid LG1 and the light grid LG2 simultaneously their Evaluate protective fields and at the same time their switching signals on the output safety-related outputs OSSD_LG1 and OSSD_LG2. This is possible, for example, when the light grids LG1 and LG2 can not interfere with each other optically. This can for example be accomplished by the fact that the transmitter two light grids LG1 and LG2 are mounted such that their Beam directions are opposite to each other, so that the Transmission light of the transmitter of the light grid LG1 not in a receiver of the light curtain LG2 can pass or by the individual transmitters have different beam encodings.

Also Here, once a light curtain LG1 or LG2 has an object in its Detected protective field, an object detection signal on the common safety-related Output OSSD be output. Is from the light grid LG1 Object detected in the protective field, so there is an object detection signal with the level of 0 V at the safety-related output OSSD_LG1 at. This signal also needs only a single one in this case Light curtain LG1 switched to the safety-related output become. The light grid LG2 can be controlled by the read back unit OSSD_MON2 notice this signal and provided with its own Signal for the safety-related output OSSD_LG2 to compare. If the light grid LG2 detects an object, would It also sets the signal level from 0 V to the safety-related output Switch OSSD_LG2. But since this already by the light grid LG1 has happened, the switching stages of the light grid LG2 are not so that the safety-related output OSSD_LG2 is potential-free is switched. However, the light grid LG2 becomes an object detected, the light grid LG2 switches through the internal switching unit CTRH2 a level of 0 V to the safety-related output OSSD_LG2.

This Level of 0 V overrides the level of 24 V, which from the light grid LG1 to the safety-related output OSSD_LG1 would switch if this would not detect an object. This ensures that an actuator of the safety-related Output OSSD is switched off. Via the control line TOKEN is the light grid LG1 informed that an object detection signal was output on the safety-related output OSSD. The Light grid LG1 can then switch back the internal switching unit CTRH1, to take back the free signal. This avoids that unnecessary currents from the light curtain LG1 over the safety-related output OSSD to the other light grid LG2 flow.

If a free signal of 24 V is present at the safety-related outputs OSSD_LG1 and OSSD_LG2, it is provided according to the invention that the control and evaluation unit 2 respectively. 2 ' one of the light curtains LG1 and LG2 outputs to the safety-related output OSSD test pulses. These test pulses cause the safety-related output OSSD to be briefly switched to 0 V for a short time, for example a period of 50 to 300 μs, and in a time interval of 2 to 10 times per second. This ensures that the safety-related output OSSD could assume the switching state object detection signal of 0 V. If, for example, the signal level remained constantly unchangeable due to a short circuit, this short circuit would be detected by this test pulse. The test pulses are read in by the read-back unit OSSD_MON1 or OSSD_MON2 and by the control and evaluation unit 2 respectively. 2 ' evaluated.

In 2 are the signals of the safety-related outputs OSSD_LG1, OSSD_LG2 or OSSD as well as the control line 8th of the two light curtains LG1 and LG2 1 in a timing diagram according to the second embodiment, according to which both light grids LG1 and LG2 make a protective field evaluation at the same time, reproduced. Here, the light grid LG1 first assumes a master or host function and the light grid LG2 a slave or guest function The signal SF_LG1 indicates the state of the protective field of the light grid LG1. The signal SF_LG1 can assume two states of protection field, free and protection field, injured. The signal S_OSSD_LG1 indicates the state of the safety-related output OSSD_LG1 of the light grid LG1. This signal S_OSSD_LG1 can assume two signals, namely 0 V, 24 V, and a floating state. The third line shows the protective field signal SF_LG2 of the light grid LG2. As with the light grid LG1, this signal can accept the states free or injured. The signal S_OSSD_LG2 of the safety-related output OSSD_LG2 of the light grid LG2 is indicated in the fourth line. In line 5, the signals S_TOKEN the control line TOKEN between the two light grids LG1 and LG2 are specified. The signals S_TOKEN of the control line TOKEN can either assume the states logical ZERO or ONE. On the control line TOKEN, a dynamic signal pattern is emitted by the light grid LG2 as long as the protective field of the light grid LG2 is not damaged. However, as soon as an object is detected by the light grid LG2, a permanent level, ZERO` is output on the control line TOKEN for communication to the light grid LG1. The last line of the time diagram shows the state S_OSSD of the connected common safety-related output OSSD of the two light grids LG1 and LG2. The safety-related, jointly connected output OSSD can in this case assume the states of the object detection signal, that is to say 0 V, and the free signal, 24 V.

In Column A is the protective field SF_LG1 of the light grid LG1 free and also the protective field SF_LG2 of the light grid LG2 shows the state free on. The light grid LG1 gives a free signal at this time at the output OSSD_LG1 off. The light curtain LG2 gives on his safety-related output OSSD_LG2 indicates a potential-free state, which in practice also as tristate, according to a third state next 24 V and 0 V, is called. The common safety-related Output OSSD thus has a signal level of 24 V, which is the Free signal corresponds. This condition is shown in columns B and C retained.

In Column D indicates the state in which the protective field SF_LG1 of the light grid LG1 is injured by an object. Thereupon switches the light grid LG1 its safety-related output OSSD_LG1 to the state object detection signal, namely 0 V, whereby also the signal S_OSSD of the connected common safety-related Output OSSD is switched to 0V. A connected actuator is then turned off and stopped a dangerous movement. From the light grid LG2 continues no signal S_OSSD_LG2 on the safety-related output OSSD_LG2, since there is no change the protective field state is present. This state is in the columns Retain E and F.

According to column G and H, the protective field of the light grid LG1 has become free again, as a result of which the associated safety-related output OSSD_LG1 is again switched to the free signal, in this case 24 V, the common safety-related output OSSD is also re-enabled. If there is a protective field violation of the light grid LG2, as shown in column I, this is the light grid LG1 on the Steuerlei TOKEN notified by no more dynamic signal pattern than signals S_TOKEN are output on the control line. The safety-related output OSSD_LG2 of the light grid LG2 is now supplied with 0 V, which corresponds to the object detection signal. In parallel, the light grid LG1 responds to the absence of the dynamic signal pattern by outputting an object detection signal at its safety-related output OSSD_LG1. Starting from the object detection of the light grid LG2, the common safety-related output OSSD is supplied with 0 V. This state is maintained for columns I to M. An additional object detection signal at the output OSSD_LG1 through the light grid LG1 in the columns J to L ultimately has no effect because the common safety-related output OSSD already has an object detection signal. Also in column M, in which the protective field of the light grid LG1 is free again, the object detection signal of the connected common safety-related output OSSD is maintained, since the protective field of the light grid LG2 is still injured.

In Column N are the protective fields of both light grids LG1 and LG2 free again. The light grid LG1 gives on the safety-related Output OSSD_LG1 the associated signal S_OSSD_LG1 of 24 V off, if the own protective field is free and it from the light grid LG2 receives the dynamic signal pattern as signals S_TOKEN, according to which the protective field of the light grid LG2 is free. This condition remains according to column O obtained. According to column P comes However, there is an interruption of the protective field of the light grid LG2, whereby the safety-related output OSSD_LG2 of the light grid LG2 is supplied with 0 V and thereby the common safety-related Output OSSD has a voltage level of 0 V, resulting in the shutdown of the actuator leads.

A surveillance of the safety-related output is in principle by two independent measures reviewed. First edge or level controlled via the common safety-related outputs. Only the host / master can output a free signal on its safety-related output. The output of the free signal takes place via the semiconductor circuit with a current limit so that every slave / guest will be able to is to override this level of the 24 V signal. In this case, the control and evaluation unit becomes an OSSD request signal generated. The master / host becomes the common safety-related one Output monitors and responds to a drop in voltage level, by the master / host opening its second switching unit and the 24 V signal is no longer on the common safety-related Output turns on. This ensures safe operation of the safety devices guaranteed.

Secondly is to increase reliability and avoidance high cross currents between the safety devices on the common safety-related output the control line provided between the master / host and the slave / guest. The guest reports the status of the protective field to the host. Report the guest or guests that their protective fields are free, so are the switching stages of the guests not activated and it is a potential-free state taken, so that the common safety-related output determined and operated only by the host and with its switching stages becomes.

reports the guest no longer that his protective field is free, so has the Host a defined time in which he has his second switching unit can deactivate, since after this time the guest its first Switching unit activated and an object detection signal with the Value 0 V switches to the common safety-related output. This avoids cross-flow between host and guest.

Should the host does not respond to the signals sent by the guest on the control line react, then the common safety-related output but immediately overwritten by the Guest. in this connection flows though a cross-flow from the host to the guest, however, takes place an immediate shutdown by a drop in voltage level and the output object detection signal.

Stay the signals from the guest on the control line continue to go out and the voltage level on the safety-related output drops The host as token owner actively switches the first one Switching unit to an object detection signal of 0 V on the switch safety-related output.

is the protective field of the guest is free again, so the guest switches his first switching stage off again, so that a potential-free state from the guest. Next the guest sends on the control line again valid signals. Are these signals from the Master detected, this switches its safety-related Output in the case of a free protective field back to a free signal from 24 V.

1, 1'

security device

2

Tax- and evaluation unit

4

system

LG1

light Curtain 1

LG2

light Curtain 2

SF_LG1

signal Protective field light curtain 1

SF_LG2

signal Protective field light curtain 2

OSSD_LG1

safety-related Light curtain exit 1

OSSD_LG2

safety-related Output light curtain 2

S_OSSD_LG1

signal safety-related output light curtain 1

S_OSSD_LG2

signal safety-related output light curtain 2

TOKEN_IN

control input

TOKEN_OUT

control output

TOKEN

control line

S_TOKEN

signal

OSSD

safety-related output

S_OSSD

signal safety-related output

OSSD_MON1, OSSD_MON2

Readback unit

A to Q

columns

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 1493064 B1 [0004]
• - EP 1262021 B1 [0004]

Cited non-patent literature

• - EN 954 [0003]
• - EN 61508 [0003]
• - EN / IEC61131 [0013]

Claims (13)

Safety device with - a control and evaluation unit ( 2 . 2 ' ), - at least one safety-related output (OSSD_LG1, OSSD_LG2) for switching an actuator, wherein the control and evaluation unit ( 2 . 2 ' ) is designed to output switching signals on the safety-related output (OSSD_LG1, OSSD_LG2), characterized in that - the control and evaluation unit ( 2 . 2 ' ) has a read back unit (OSSD_MON1, OSSD_MON2) to read back switching signals on the safety-related output (OSSD_LG1, OSSD_LG2). Security device according to claim 1, characterized in that the control and evaluation unit ( 2 . 2 ' ) is designed to read in and / or output control information on a control line (TOKEN). Safety device according to one of the preceding Claims, characterized in that the safety-oriented Output (OSSD_LG1, OSSD_LG2) is not only designed to handle the switching signals, namely an object detection signal or a free signal, but also designed to be a potential-free To take state. Safety device according to one of the preceding Claims, characterized in that the safety-oriented Output (OSSD_LG1, OSSD_LG2) a switching voltage of 0 V to 3.5 V when an object detection signal is applied and a Switching voltage of 24 V with a tolerance of + -2.5 V. has, when a release signal is output, at a switching current from 0 to 600 mA. Safety device according to one of the preceding claims, characterized in that the control and evaluation unit ( 2 . 2 ' ) a semiconductor circuit ( 6 . 6 ' ) comprises at least two switching units each (CTRL1, CTRH1, CTRL2, CTRH2), wherein a first switching unit (CTRL1, CTRL2) is designed for switching the object detection signal and a second switching unit (CTRH1, CTRH2) is designed for switching the free signal. Safety device according to one of the preceding claims, characterized in that the control and evaluation unit ( 2 . 2 ' ) has two channels. Safety device according to one of the preceding claims, characterized in that the control and evaluation unit ( 2 . 2 ' ) is designed to apply test pulses to the safety-related output (OSSD_LG1, OSSD_LG2). Safety device according to one of the preceding Claims, characterized in that this safety switching devices or safety controllers are. Safety device according to one of the preceding Claims 1 to 6, characterized in that this optical Sensors, in particular light barriers or light grids (LG1, LG2) are. System with at least two security devices ( 1 . 1' ) for generating safety-related signals, characterized in that the safety devices are designed according to one of the preceding claims and can be connected to one another via their safety-related outputs (OSSD_LG1, OSSD_LG2). System according to claim 11, characterized in that that the security devices have a control line (TOKEN) are connected to each other. System according to claim 11, characterized in that that a release signal of the first or second safety-related Output (OSSD_LG1) by an object detection signal of the second or the first safety-related output (OSSD_LG2) can be overwritten is. System according to one of the preceding claims, characterized in that test pulses are generated by the control and evaluation units ( 2 . 2 ' ), alternately only from a single safety device ( 1 ).