1746-OB16 SLC500 SLC 500 ALLEN-BRADLEY ALLENBRADLEY NEW USED plc Allen-Bradley 1746-OB16 SLC 500 OB16 module Allen-Bradley SLC 500 Digital DC output 16-channel 24V DC output module SLC Current sourcing DC output Allen-Bradley Output module 16 points Industrial automation output module PLC digital output module 1746-OB16 Transistor sourcing output 10-50V DC SLC 500 I/O module output