Can't help much here but found the answer to your original question.
Found here:
http://www.connectworld.net/cables/scsifaq.html
Extract:
"-Single ended:
"Normal" electrical signals. Uses open collector to the SCSI bus, [usually]
survives wrong cable insertion. DIFFSENSE signal is used to detect
connection of wrong type devices.
The max. length for SCSI-1 is a 6 meter
cable with stubs of max 10cm allowed to connect a device to the main-cable.
Most devices are single ended."