It gets a bit more interesting around the back.

On the left is the click-button for setting the drive number, currently set at 0, then the daisy-chain arrangement of Centronics SCSI ports. At the top a socket for connecting a further FileStore hard disc unit, either an E40S or an E60S, and at the bottom a short lead to go to the E01S.

There is also a daisy-chain power arrangement on the right along with the on/off switch.