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 secondary 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 seconds 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.

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

 

 

 

 

 

 

2

 

 

 

 

 

 

A

2

C

Figure B-2

Three-Wire Minute Impulse (59th Minute)

B-4

24A715/24A715M Master Clock Installation Manual