2019 California Standards for Accessible Design Guide (effective January 1, 2020 with July 1, 2021 amendments)

1009.8.1 System requirements.

Two-way communication systems shall provide communication between each required location and the fire command center or a central control point location and a central control point is not a constantly attended location, a two-way communication system shall have a timed automatic telephone dial-out capability to a monitoring location or 9-1-1. The two-way communication system shall include both audible and visible signals.

1009.8.1.1 Visible communication method.

[DSA-AC and HCD 1-AC] A button complying with Section 1138A.4 or Sections 11B-205 and 11B-309 in the area of refuge shall activate both a light in the area of refuge indicating that rescue has been requested and a light at the central control point indicating that rescue is being requested. A button at the central control point shall activate both a light at the central control point and a light in the area of refuge indicating that the request has been received.