Specifications

53
Schneider Electric
Interfaces (continued)
Definition: The modulation speed of the modem must not be confused with the
speed of the COM port on the computer. Modem speed represents the rate of
transfer of DCE, while COM port speed represents the transfer rate of DTE.
Modem communication speed can be changed during an exchange according to
load on the telephone network. For high speeds, use of RTS/CTS "hardware" flow
control is recommended.
Installation recommendations
Hardware:
b Modems are normally delivered with a telephone connection cable and a serial
connection cable for connecting to the PC/Mac/terminal.
b Refer to supplier instructions when installing a PCMCIA modem.
b Connect the telephone cable to the LINE outlet (and not the PHONE outlet) on the
modem. (Other terms are sometimes used.)
b Connect the serial cable to the RS232 outlet on the modem and the PC/Mac/
terminal.
b Connect the outside power supply first to the 220 V line and then to the modem.
(First make sure the modem is set to the OFF position.)
Software:
b The software provided with the modem cannot generally be used to perform tests.
Thus we recommend that a terminal emulator be used to perform the first operating
tests.
b A driver and installation instructions are provided with PCMCIA modems. Refer
also to drivers installed on the PC operating system.
Serial connection with the modem:
b Once the modem has been turned on:
v verify that the modem has passed tests successfully and is in READY mode (ready
to operate according to its LEDs),
v configure the terminal emulator (or the terminal) with the maximum baud rate
supported by the modem or the PC/Mac/terminal.
- choose 9600, 19,200, 38,400, 57,600 or 115,200,
- choose 8 data bits, 1 stop bit and parity none (8, 1, N or 8N1).
v type the command AT [ENTER] and verify that the modem responds OK. If this is
the case, the PC/Mac/terminal and modem link are already operating (but without
any real flow-control test).
Connection with the telephone line:
b Now that your emulator is communicating with the modem:
v type the command ATDP161 [ENTER],
v the modem will dial the number; you should hear the talking clock in the modem’s
speaker.
v the modem <-> telephone line link is in order.
v you can then use a CARPE number (or the number of another service provider) to
test the connection with data.
v at this point, if everything is operating properly, part of your installation has been
completed.
Billing pulses will disturb the modem if they are not filtered (in the modem, with an
external filter or by your telecommunications service), particularly if there is no error
correction.
General characteristics:
b Industrial or office modem (depending on
use).
b Analogue/Digital (depending on
connection to the telephone network).
b Adaptable transmission speed (on the
telephone network).
b AT commands accepted for use and
parameter setting.
b RS232 input available (speed compatible
with MODBUS).
b Dry contact input available to initiate a
call.
b Conformity with EMC directives.
The most frequently encountered problems
with serial connections are poorly suited
speed and cables that cannot support
hardware flow-control.
The most common problems with
telephone connections are:
b Unsuitable telephone cables (not
adapted to the Swiss standard, for
example).
b Wall jack incorrectly cabled.
b The telephone is connected:
v to a double jack with 2 telephones,
v to a special fax / telephone line,
v to a private exchange.
Guide to Integration
Modbus / Jbus