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 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.

X = Normally open contact

I = Normally closed contact

2 = 1N4004 diode or equal

RELAY

K6 (K8)

x

CLK1 OR CLK2

1 2

10 ASB MAX.

+

24Vdc

–

 

 

RELAY

 

 

 

 

 

K5 (K7)

 

 

 

 

I

 

 

I

 

 

 

x

 

 

x

 

 

 

 

 

 

 

 

MASTER CLOCK

3

4

5

6

7

8

FIELD CONNECTIONS

 

 

 

 

 

 

 

 

 

 

 

 

B

 

 

 

 

 

 

A

2

 

 

 

 

 

2

 

 

 

 

 

 

C

Figure B-23

Three-Wire Minute Impulse (44th Minute)

B-26

24A715/24A715M Master Clock Installation Manual