This is a very "Old-School" PLC 24V interface with NTE 8-Blade, DPDT Relays on sockets mounted to a box. Inside the cover you will notice the coil back EMF diodes and the contact supression diode mounted to the relay socket. Phoenix panel-mount connectors were used to get all the I/O into the box. It includes LED indicators for coil activation and a fuse for 24V power. Of course these days all this stuff can be purchased as integrated on a DIN rail socket, but as I/O goes, this box is almost bullet-proof. It was designed as a module so the Phoenix terminal blocks could be removed and the unit repaired with low impact to the machine. The relays can be replaced on the sockets with ease.