Source Number - IBM RT PC 10 Hardware Maintenance And Service

Source Number
The left two digits of the SRN is the source number. The left digit of the
source number identifies the device. The right digit of the source number
identifies the procedure that produced the SRN. The following chart
identifies the devices and procedures. Use the following SRN for an
example.
13 - 234 - 100 - B34 - D64
Device Procedure
2-18 Service Manual
1 - System unit
2 - Display
3 - Keyboard
4 - Tape drive
5 - Printer
6 - Reserved
7 - Reserved
8 - Reserved
9 - Reserved
0- Reserved
1 - Resident POST program
2 - Loadable POST program
3 - Standalone diagnostic program
4 - Licensed program product
5 - Support center
6 - Problem determination procedures
7 - Reserved
8 - Reserved
9 - Reserved
0- Reserved