NEC SL1100 - Page 521

Operation
To mute your telephone handset or Handsfree microphone while on a call:
1. Press Mute key.
To turn your telephone microphone back on:
1. Press Mute key.
Use Mute key only if you pressed it initially to turn off your Handsfree microphone.
ISSUE 2.0 SL1100
Features and Specifications Manual 1-509
M