AT&T Merlin 820 Service And Maintenance Manual page 40

On both voice terminals, perform the action that revealed the trouble.
Step 7.
IF
The trouble appears on the voice
terminal on which it first
appeared,
The trouble appears on the voice
terminal that at first did not have
the trouble,
Switch the handset cord of the voice terminal on which the trouble
Step 8.
appears and the handset cord of the voice terminal with no trouble (see
Figure 13).
HANDSET CORD
(VOICE TERMINAL
WITHOUT TROUBLE)
Figure 13—Switching Handset Cords
Trouble on One Voice Terminal
THEN
The handset is not causing the
trouble. Replace the handsets as
they were and go to Step 8.
Trouble found. It is caused by
the handset on which the trouble
now appears.
Read the section on Maintenance
Exchange Procedures at the end of
this manual.
HANDSET CORD
(VOICE TERMINAL
WITH TROUBLE)
Page 37