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TYPE 20—Three-Wire Minute Impulse (44th Minute)
Every minute, from the 58th second to 00 seconds, a 24Vdc pulse is transmitted to the
secondary clocks. From the 44th minute through the 34th minute, the pulse is transmitted
on the A and B lines. From the 35th minute to the 44th minute, the pulse is transmitted on
the A line only. Clocks that reach the 44th minute ahead of the master clock stop, since at
this time they respond only to pulses transmitted on the B line. During the 44th 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.
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-26
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
2
24Vdc
2
Figure B-23
Three-Wire Minute Impulse (44th Minute)