Wiring the Communications Terminal Block

The communications terminal block is on the back of the display unit. See Figure C-6. It is used to connect the optional modem, a computer, any RS-485 devices, and a power source for the optional remove schedule selector.

 

1

2

3

4

5

6

7

8

9

10 11 12 13

 

TxD

G

RxD

D

D

G

S

D

D

D

D

~ ~

 

 

N

 

+

-

N

Y

+

-

+

-

 

 

 

D

 

D

N

12V~

MODEM

RS-232

RS-485

 

C

SYNC

SYNC

 

AC

HOST COMMUNICATIONS

 

PULSE

OUT

IN

 

OUT

 

SYNC

 

RS-485

 

 

 

 

 

 

 

 

 

250ma

DATA SYNC

Figure C-6

The Communications Terminal Block

When making connections to the communications terminal block, keep the following in mind:

•Twisted-pair (Cat-3/Cat-5) wire connects directly to the terminal block, with up to two wires per position.

•The pulse-sync input is the same as provided in the power supply. A one-second (minimum) dry-contact switch closure across the terminals will cause the master clock to reset the time to 12:00 AM of the nearest date.

•Grounds (GND) are signal grounds, not chassis grounds.

Wiring the Host Communications Terminals

The host communications terminals on the communications terminal block include:

RS-232—Three terminal block contacts for RS-232 communications with an IBM- compatible computer running the optional Lathem MasterLink programming software.

Notes:

This terminal is typically used for a permanent connection to a computer. To make a cable to connect the computer to the RS-232 terminals, see Figure C-7on page C-5.

For a temporary computer connection, see Connecting a Computer to the Front Access Port on page C-8.

C-4

24A715/24A715M Master Clock Installation Manual