AT&T Partner II Installation And Use Manual page 23

Speakerphones provide hands-free two-way operation of a phone
without lifting the handset. Combining a speakerphone with an
MLS-model phone or a standard phone on an extension in a conference
room or office is an inexpensive way for several people at a meeting to
conference with other parties. The equipment controller supports the
AT&T S203 speakerphone. (MLS-model phones have built-in speakers,
but they are designed for individual—not group—use.)
Repertory dialers allow you to store frequently-used numbers for
one-touch dialing (Auto Dialing). If a user needs many Auto Dial
numbers, a repertory dialer can be combined on an extension with an
MLS- or MLC-model phone or standard phone.
Headsets allow users to hold private, hands-free conversations. A
headset is a combination earphone and microphone worn on the head,
useful for receptionists, salespeople, or others who need to have their
hands free while talking on the phone. AT&T offers several compatible
headsets.
Handsets for the hard-of-hearing are designed for users who need
even more amplification than is provided by the volume controls on MLS-
and MLC-model phones. Although the volume controls on MLS- and
MLC-model phones significantly reduce the need for an amplified
handset, hard-of-hearing users may find that the AT&T K6S handset
meets their needs.
1-12 Overview