IBM Personal Computer Manual To Operations page 157

Test 2000
Do you have an IBM Binary Synchronous
Communications Adapter installed in your system?
NO - Continue with the next Test.
YES - Did any of the following error messages appear
on your screen?
XX:XX:XX
ERROR - SYSTEM UNIT 20XX
XX:XX:XX
ERROR - SYSTEM UNIT 21XX
XX:XX:XX
ERROR EXPANSION UNIT 20XX
XX:XX:XX
ERROR EXPANSION UNIT 21XX
YES - Have the unit that contains the adapter
serviced.
NO - Your system has completed this test
successfully. Continue with the next Test.
April 1984
Test 2000-1