(under subclass 501) Subject matter together with means to effect a change in the indication to further indicate that the condition has been noted.
(1) Note. Acknowledgement exists when a remote office sends an alert signal in response to the sensed condition to a central office where the signal is indicated; and the central office then responds with an acknowledgement signal (which may or may not return to the remote office), which causes a change in the indication at the central office. This should be distinguished from interrogation which occurs when the controller at the central office sends an interrogating signal such as pulse or code to the remote office, and the remote office returns a signal indicative of the original signal and any intervening disturbances. This should also be distinguished from "answer-back" which occurs when the remote office sends an alarm signal to the central office, and the central office returns a signal indicative of the successful completion of the alarm function.
