plc BECKHOFF BECKHOFF PLC bus terminal DIGITAL INPUT DIGITAL KL1512 KL 1512 BECKHOFF ANALOG MODULE PLC KL1512 BECKHOFF PLC KL1512 BECKHOFF KL1512 BECKHOFF KL 1512 ANALOG MODULE PLC KL1512 kl1512 beckhoff kl-1512 beckhoff kl1512 digital input beckhoff kl1512 2 channel