Adtran TRC4108 Manual Do Utilizador

Section 3  Engineering Guidelines

TRACER 4108/4208 System Manual

 30

© 2003 ADTRAN, Inc.

612804208L1-1B

Modem controls, discussed in Section 5, User Interface Guide, enable or disable modem control
through the RS-232 interface. When this option is enabled from a standard terminal connection, all
RS-232 communications cease until a modem with a null modem adapter is attached between the 
TRACER 4108/4208 and the data modem. Configure the data modem for 

 and 

. 

When the user connects via the modem to the TRACER 4108/4208 unit, communications via the RS-232 
port resume. If a user accidentally enables modem control from a terminal and disrupts the RS-232 
communication, pressing <Ctrl + Z> three times will temporarily disable the modem control option (until 
the system is reset) and will access the system option to disable modem control.

The TRACER 4108/4208 must be interfaced to a modem via an RS-232 null modem adapter or cable. The 
null modem converts Clear To Send (CTS) and Data Set Ready (DSR) into Ready To Send (RTS) and Data 
Terminal Ready (DTR), respectively. These signals indicate (to most modems) that a valid DTE terminal 
device is present. The null modem interface must route Carrier Detect (CD) on pin 8 directly from the 
modem. When using the RS-232 interface for modem control, the modem must source CD only when 
actually connected to a carrier.

When 

is selected in the menu system, the TRACER 4108/4208 will de-assert DTR 

and DSR for a time greater than 20 msec. The null modem consequently drops DTR and RTS at the 
modem interface, signaling the modem to hang up the line. If password functionality is enabled in the 
TRACER 4108/4208, selecting 

 resets the TRACER 4108/4208 to the password entry 

screen.

Table 5 contains the wiring diagram needed for connecting the TRACER 4108/4208 RS-232 interface to a 
modem using the null modem adapter.

2

TX

3

RX

3

RX

2

TX

4

RTS

5

CTS

5

CTS

4

RTS

6

DSR

20

DTR

7

GND

7

GND

8

CD

8

CD