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TYPE 02—Two-Wire Reverse Polarity Minute Impulse (59th Minute)
There are two kinds of Type 02 secondary clocks: the two-wire reverse polarity minute im
-
pulse covered on this page, and the three-wire minute impulse on the previous page.
Note:
For a list of Type 02 clocks, see the chart on the first page of this appendix.
Every minute, from the 58th second to 00 seconds, a 24Vdc pulse is transmitted to the
secondary clocks. From the 59th minute through the 49th minute, the pulse is transmitted
with line AB positive with respect to PC. From the 50th minute to the 59th minute, the pulse
is transmitted with line AB negative with respect to PC. Clocks that reach the 59th min
-
ute ahead of the master clock stop, since at this time they respond only to pulses
transmitted with line AB positive with respect to PC.
During the 59th minute, from 10 seconds through the 50th second, 20 rapid pulses are
transmitted at 0.5Hz to advance all slow clocks. During the rapid pulsing, line AB is neg
-
ative with respect to PC. Connect a diode as shown in Figure B-3 for arc suppression of
the relay contacts.
An accumulator, designed in the software, counts the number of minutes lost due to
power failure. When power is restored, the master clock transmits pulses with line AB
positive with respect to PC 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
with line AB positive with respect to line PC. The remainder of the pulses are transmitted
with line AB negative with respect to line PC. Normal minute pulses are inhibited during
these pulses.
24A715/24A715M Master Clock Installation Manual
B-5
12345678
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
24–36 Vdc
+
10 ASB MAX.
–
AB
PC
2
= 1N4004 diode or equal
2
1
= V250LA4 MOV or equal
1
Figure B-3
Two-Wire Reverse Polarity Minute Impulse (59th Minute)