Brother FAX 1840C - Manual (Page 184)

APPENDIX A A - 12
When you are using a TAD, the LCD shows Telephone
(MFC-3240C and MFC-3340CN only) or Ext. Tel in Use
(FAX-1840C and FAX-1940CN only).
Connections
The external TAD must be plugged into the back of the machine, into
the jack labeled EXT. Your machine cannot work properly if you plug
the TAD into a wall jack (unless you are using Distinctive Ring).
1
Plug the telephone line cord from the telephone wall jack into the
back of the machine, in the jack labeled LINE.
2
Plug the telephone line cord from your external TAD into the
back of the machine, in the jack labeled EXT. (Make sure this
cord is connected to the TAD at the TAD’s telephone line jack,
and not its telephone jack.)
If You Do Not Subscribe to Distinctive Ring Service:
You must plug your TAD into the EXT. jack of your machine. If
your TAD is plugged into a wall jack, both your machine and the
TAD will try to control the phone line. (See illustration below.)
Unless you are using Distinctive Ring, do not connect a
TAD elsewhere on the same phone line.
TAD
TAD