Settings
Alert sensitivity and quiet period. These apply to both phones.
Alert threshold
How loud (and for how long) before alerting.
Alerts
When the baby's-room phone crosses the threshold, your phone (the receiver) rings loudly and flashes.
After you dismiss an alert, no new alerts fire for this many minutes (prevents alert spam while you're attending to the baby).
Rings any armed receiver phone right now (bypasses the quiet period), so you can confirm it works.