BECKHOFF TwinSAFE - Manual (Page 136)

Circuit examples
134 Application Guide TwinSAFE
2.23 Direct wiring of the TwinSAFE outputs to TwinSAFE
inputs (2-channel) (Category 3, PL d)
Two outputs of an EL2904 are wired directly to two safe inputs of an EL1904; the test pulses and current
measurement of the outputs and the sensor test of the inputs are thereby deactivated. On the input side,
both signals are checked for discrepancy within the TwinSAFE logic. Hence, both signals are checked for
their value, but no tests are active on the cable, so that possible external feeds are detected when
switching the outputs.
2.23.1 Parameters of the safe input and output terminals
EL1904
Parameter Value
Sensor test channel 1 active No
Sensor test channel 2 active No
Sensor test channel 3 active No
Sensor test channel 4 active No
Logic channel 1 and 2 Single Logic
Logic channel 3 and 4 Single Logic
EL2904
Parameter Value
Current measurement active No
Output test pulses active No
2.23.2 Block formation and safety loops
2.23.2.1 Block 1
EL6900 EL2904 EL2904 EL1904
EL2904 EL1904