This is the FileStores from the back. The E01S main unit is at the bottom and the E40S hard disc unit on top. The E01S has a Centronics-type SCSI connector at the back for connecting hard disc units. Up to four E40S and E60S hard disc units can be connected to one FileStore E01S, in a daisy chain arrangement.

The FileStore E40S has a black cable with Centronics connector coming out of it and another Centronics port for the next unit. The power leads are also daisy-chained as can be seen in the picture.