ADC-A12C31 Operator’s Handbook Rev. A P. 16
The ADC-A12C31 analog clock provides flexible configuration options supporting most world DST
standards.
Pre 2007 Standard – U.S.A. and Canada
Traditional US/Canada daylight/summer time is configured as one (1) hour positive offset.
For the U.S. (through 2006) and Canada, daylight savings time begins on the first Sunday of
April at 2:00AM (Local Time) and ends on the last Sunday of October at 2:00AM (Local
Time).
Post 2006 Standard – U.S.A. and Canada
On August 8, 2005, the Energy Policy Act of 2005 was signed. This Act changed the time
change dates for Daylight Saving Time in the U.S, effective in 2007. DST now begins on the
second Sunday of March at 2:00 AM (Local Time) and end the first Sunday of November at
2:00 AM (Local Time).
EU Standard – European Union
In the European Union, daylight change times are defined relative to the UTC time of day
instead of local time of day (like in the U.S.). For the European Union, summertime period
begins at 1:00 AM UTC on the last Sunday of March and ends at 1:00 AM UTC on the last
Sunday of October. Please carefully consult the section entitled “Device Settings” for details
on setting daylight time.
To ensure proper hands-free year-around operation, DST adjustments must be configured
using the daylight time option and not with the time zone offset option.
Freewheeling Accuracy
The ADC-A12C31 has built-in provisions to allow the clock to freewheel and maintain accuracy for
extended periods in the absence of time code. These features also allow the unit to be set manually
and operate without time code.
TCXO and RTC circuit
The ADC-A12C31 contains a precision TCXO and RTC circuit allowing the clock to maintain an
accuracy of +/- 1 minute per year to the last known time code input (+/- 165 mS per day)
when time code is not preset or cannot be decoded (i.e. freewheeling mode).
Maintenance-free Rechargeable Battery
The RTC and TCXO are maintained continuously from a rechargeable battery circuit during
periods of power outage. Minimum holdover period is two weeks once the battery is
charged. The battery will automatically charge when the unit is next powered and requires
no maintenance.
Non-Volatile Configuration
The clock configurations are maintained in non-volatile memory allowing the current settings to be
retained during power outages.
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