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TYPE 02—Three-Wire Minute Impulse (59th Minute)
There are two types of Type 02 secondary clocks: the three-wire minute impulse covered on
this page, and the two-wire reverse polarity minute impulse on the following page.
Note:
For a list of Type 02 clocks, see the chart on the first page of this appendix.
From the 58th second to 00 seconds each minute, a 24Vdc pulse is transmitted to the sec
-
ondary clocks. From the 59th minute through the 49th minute, the pulse is transmitted on
both the A and B lines. From the 50th minute to the 59th minute, the pulse is transmitted
on the A line only.
Clocks that reach the 59th minute ahead of the master clock stop, since at this time they
respond only to the pulses transmitted on the B line. During the 59th minute, from 10 sec
-
onds through the 50th second, 20 rapid pulses are transmitted at 0.5Hz on the A line to
advance all slow clocks.
An accumulator, designed in the software, counts the number of minutes lost due to
power failure. Upon resumption of power, the master clock transmits pulses on lines A
and B to immediately advance the slow clocks to the proper time. Resetting the time after
a power failure terminates these correction signals.
Manual clock advances and daylight saving advances cause the master clock to transmit
62 pulses (1 second ON and 1 second OFF at 0.5Hz). The first five pulses are transmitted
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-4
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
24Vdc
+
10 ASB MAX.
–
B
A
2
= 1N4004 diode or equal
C
2
2
Figure B-2
Three-Wire Minute Impulse (59th Minute)