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Coded switches are virtually impossible to defeat

The PSENcode series is designed for applications conforming to the requirements of EN 954-1 Category 4. Three types of switch are available, with the uniquely coded version having a matched switch and actuator that will only work in combination with each other. Virtually impossible to defeat, the switch provides an exceptional level of integrity.

But the advantages of the coded switches do not end there: huge cost advantages can be gained on machinery fitted with multiple opening guards. Whereas a Category 4 application would normally require two mechanical switches per guard (to ensure mechanical redundancy), each connected to a separate channel on a safety relay (for electrical redundancy), as many as ten or more PSENcode switches can be connected in series, all monitored by a single relay. This leads to considerable savings on hardware costs, as well as substantially simplified wiring. Indeed, the switches can be connected to a Pilz PNOZ X-range electromechanical relay, a PNOZelog microprocessor-based monitor, a PNOZmulti software-configurable modular safety controller, a Pilz PSS (programmable safety system) or a SafetyBUS p safe fieldbus network.

In addition, the 24V DC switches have a signal output that can be connected to a PLC, operator display or other process controller so that an operator can immediately identify which guard has been opened. Each switch also has three high-brightness LEDs that aid fault diagnosis.

Nevertheless, the switches use dual microprocessors and solid-state transponder technology (the same as in RFID tags), with no moving parts, so they should last at least as long as the machine on which they are installed. Should the switch sustain any physical damage, it can be replaced quickly thanks to the use of M12 plug-in connections - and the use of metal threads ensures that even the electrical connection is extremely robust.

Depending on the level of switch integrity required, Pilz offers three types of switch, all with a fast 20ms response time: the coded model (PSEN cs1.1p) operates with any compatible Pilz actuator; the fully coded model (PSEN cs2.1p) has a facility to teach-in a new actuator in the event of loss or damage (restricted to eight times to reduce the risk of tampering); and the uniquely coded model (PSEN cs2.2p) can only ever be used in conjunction with the actuator with which it is supplied. In all cases the actuator can approach the switch from any of five directions, with a switching distance of 17mm that ensures reliable operation even when guard mountings start to wear and cause the switch and actuator to become misaligned. For hygienic applications or where it is desirable to conceal the switches to deter attempts to defeat them, the switch and actuator can be covered by non-metallic materials with no affect on the performance. Furthermore, the switches are fully protected so that they cannot be damaged as a result of wiring errors.

As well as the three models described above, Pilz offers ATEX-approved versions of the coded and fully coded switches for use in Hazardous areas. All variants are sealed to IP67.


Pilz Automation Ltd
Pilz House, Little Colliers Field
Corby, Northants, NN18 8TJ
United Kingdom

Telephone: +44 1536 460766
E-Mail: sales@pilz.co.uk