JSHD4 AH is a JSHD4 bottom part with a cable gland and 10 screw connections. It is used with any JSHD4 top part, except JSHD4-1, to form a complete three-position device. Three-position devices are used to allow a limited movement of the machine when the operator is in the dangerous area, for example during troubleshooting, test running and programming.