The resistance evaluator 462.4x is a safety-switching unit designed for monitoring GELBAU Contact- Duo safety connecting blocks with a terminating resistance of 8,2 kΩ. The series 462.4x is a dual- channel version including redundancy monitoring. The stop-outputs (13,14-23,24) include 2 forced safety relays and a reset-function. The additional two- way contact (31, 32, 34) is an alarm contact as well as an auxiliary contact. The safety system corresponds to standards according to ZH1/494 as well as the European standard EN1760-2 for connecting blocks corresponding to output-equipment.