The features of high-end landline handsets include:
Unspecified call blocking or silencing
Once the landline receives an anonymous call, it can either send back a busy tone to assume you are engaged. It can also bring the caller to the answering machine without any ring to avoid disturbance.
The landline gives you the freedom to add an unidentified number on the blacklist section. Calls from the blacklisted number will receive a busy tone or be sent to the answering machine without ringing.
Do not Disturb feature
You can set the phone not to ring for a specific time. When it does, the unwanted rings will become silent to the answering machine unless the caller is on the VIP list.