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TYPE 05—Three-Wire Minute Impulse (58th Minute)
Each minute, from the 58th second to 00 seconds, a 24Vdc pulse is transmitted to the sec
-
ondary clocks. From the 58th minute through the 48th minute, the pulse is transmitted on
both the A and B lines. From the 49th minute to the 58th minute, the pulse is transmitted
on the A line only. Clocks that reach the 58th minute ahead of the master clock stop,
since at this time they respond only to pulses transmitted on the B line. During the 58th
minute, from 10 seconds through the 50th second, 20 rapid pulses are transmitted at
0.5Hz on the A line to advance all slow clocks.
An accumulator in the master clock software counts the number of minutes lost during a
power interruption. When power is restored, the master clock transmits pulses on both
lines A and B to immediately advance the slow clocks to the correct time. Resetting the
time after a power interruption terminates these correction signals.
Manual clock advances and daylight saving advances cause the master clock to transmit
62 pulses (one second ON and one second OFF at 0.5Hz). The first five pulses are trans
-
mitted on lines A and B. The remainder of the pulses are transmitted on line A only.
Normal minute pulses are inhibited during these pulses.
B-8
24A715/24A715M Master Clock Installation Manual
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CLK1 OR CLK2
x
x
x
x
RELAY
K6 (K8)
RELAY
K5 (K7)
II
MASTER CLOCK
FIELD CONNECTIONS
X = Normally open contact
I = Normally closed contact
–
10 ASB MAX.
+
B
A
C
2
= 1N4004 diode or equal
24Vdc
2
2
Figure B-6
Three-Wire Minute Impulse (58th Minute)