Measurement Computing Micro 488/EX rev.2.1 - Manual (Page 190)

Section 8 IEEE 488 Primer
8.8
8.7.2 Listen Address Group (LAG)
There are 31 (0 to 30) listen addresses associated with this group. The 3
most significant bits of the data bus are set to 001 while the 5 least
significant bits are the address of the device being told to listen.
8.7.3 Unlisten (UNL)
This command tells all bus devices to Unlisten. The same as
Unaddressed to Listen. (&H3F)
8.7.4 Talk Address Group (TAG)
There are 31 (0 to 30) talk addresses associated with this group. The 3
most significant bits of the data bus are set to 010 while the 5 least
significant bits are the address of the device being told to talk.
8.7.5 Untalk (UNT)
This command tells bus devices to Untalk. The same as Unaddressed to
Talk. (&H5F)
8.7.6 Local Lockout (LLO)
Issuing the LLO command prevents manual control of the instrument's
functions. (&H11)
8.7.7 Device Clear (DCL)
This command causes all bus devices to be initialized to a pre-defined
or power up state. (&H14)