This is a feedback module for current sensors on digitally controlled 2-rail layouts. This module can be plugged into the L88 (60883) with the cable included with the former. The s 88 DC has a connecting socket for additional s 88 DC decoders (60882). It also has 2x 8 inputs for current sensors (with optical-couplers) in 2 different power circuits that can be combined into a single power circuit with 16 inputs. Highlights: Set screw terminals for all connections. Network cable included. Charlie's Tip: You use this type of feedback (S-88) decoder on two rail layouts, where you use the technique of isolating one of the two rails as track detection. When a locomotive (power user) is on that isolated piece of track, it will get it's power through the S-88 to that rail. The S-88 detects that current flows through its port to the rail, and sends a signal to the Central Station.