National Research Council Time Signal

The National Research Council Time Signal is Canada's longest running but shortest radio programme. Heard every day since November 5, 1939 (three years and three days after the CBC's establishment), shortly before 13:00 Eastern Time across the CBC Radio One network, it lasts between 15 and 45 seconds, ending exactly at 13:00. During standard time, the signal is at 13:00 Eastern Standard Time and during Daylight Saving Time, the signal is at 13:00 Eastern Daylight Saving Time.

The signal is also heard on some stations of the Ici Radio-Canada Première network at 12:00 ET daily, particularly in Ontario, Quebec and the Maritimes provinces.

The signal consists of a series of 300 ms "pips" of an 800 Hz sine wave tone, each one starting at the top of each UTC second, up to ten seconds before the hour, followed by silence, and then a one second-long 800 Hz tone to mark the top of the hour. The CBC time signal is typically delayed by about 300 ms with respect to the CHU time signal, because each CBC radio station receives the actual time signal from Ottawa by satellite.

The spoken header, as announced by a local on-air talent at each station, is typically of the style,

In different time zones, the local time and time zone is used instead. This header is usually spoken over the initial pips. As of May 2011, the length of the silence has been reduced to six seconds, with a soft click at the beginning of each second during the silence.

At the top of many other hours, and at the discretion of each station, a one-second tone is sounded, but the hour itself is not necessarily announced.

NRC runs two telephone numbers that announce the time of day. Voice announcements of Eastern Time are made every 10 seconds, followed by a tone indicating the exact time. This service is available to the general public by dialing +1 (613) 745-1576 for English service and +1 (613) 745-9426 for French service. The call is automatically cut off after 30 seconds or three announcements. Long-distance charges may apply for those calling from outside the Ottawa/Gatineau area, depending on provider.

...
Wikipedia