10
An optional GPS receiver is available for the master clock. This receiver sends the time received
from the GPS satellites wirelessly to the master clock. The GPS receiver can be used in addition
to NTP time for a redundant time source.
Configuring the Time Zone Offset
If the time displayed is incorrect after the synchronization indicator appears, then time zone rules
may require reconfiguration. Mode 21-1 determines the time zone offset from universal
coordinated time (UTC).
Configuring Daylight Saving Rules
If Daylight Saving Time is not observed in your area, set Mode 24-1 = 0.
The RC100 Master Clock offers two methods of implementing automatic switching between
Standard and Daylight Saving Time, rule based and fixed day-of-the-year. The rule based
method is preferred because it provides the correct day of the year regardless of whether it’s a
leap year or not. The rule method is configured by entering numeric values that represent the
specific rule for your area. Mode 45-20 (switch to Daylight Saving Time) and Mode 45-21
(switch to Standard Time) are used to store the Daylight Saving Rule.
The format is MMRD, where MM = month (1-12), R = instance of the select day of the week (1-
5 5=last instance), D = day of the week (1-7), where 1=Monday and 7=Sunday. For example,
357 = the last Sunday in March, and 1117 = the First Sunday in November.
If the value >2000 then the right two digits represent the day of the month. The left two digits,
minus 20, equal the month. For example, March 15th = 2315, April 1st = 2401.
To configure a fixed day of the year (example, 15
th
of the month), then set the modes to 0, and
enter the day of the year to switch into Mode 52-1 (switch to Daylight Saving Time) and Mode
52-2 (switch to Standard Time).
For a list of Daylight Saving Time rules for your area, go to www.timeanddate.com.
Connections on the back of the master clock.
