The RCS is a programmable Lego "brick." It has 3 sensors (input), ports, 3 output ports, 4 control buttons, an LCD display and an infrared transmitter. It also has a microprocessor, to action programs, an internal memory to store "firmware" and programs, and a built in speaker to produce various tones.

Being a Lego "brick," it has Lego "studs" and holes, to allow the connection of other Lego "bricks" and "pegs."

The sensor ports are used for attaching light and touch sensors, as well as other additional sensors.