Modems - Siemens milltronics BW500 Instruction Manual

Modems

The BW500 has been successfully connected to several different modems. In general, the
Modbus protocol is a very modem friendly protocol. This section gives some general
guidelines on modems and their connection. For detailed information, see the modem
documentation.
Picking Modems
There are several different types of modems; dial-up, leased line, radio-link, fiber-optic to
name the most common.
Dial-up
uses a standard analog phone line and dials the number of the receiving modem.
Lease line
come in either 2 or 4 wire types and use special phone lines that are 'leased' from your
phone company (or you) and do not require any dialing.
Radio-link
come in many different types, but all use radio frequencies for transmitting the
information.
Fiber-optic
uses a fiber-optic line to connect the two modems.
Each type of modem and each model have various characteristics. Before purchasing the
modem contact the modem manufacturer and ask if they have had experience using the
modems with Modbus protocol with no flow control. If they have, ask them what settings
were required.
Setting up the Modems
Modems can be configured using software, dip switches, jumpers or a combination.
Dip switches are normally located at the back of the modem, jumpers are normally
located on the motherboard and require that you remove the cover. Software normally
requires you to use a standard terminal program and to connect to the RS-232 port on the
modem and send special commands. The most popular command set is called the AT, or
Hayse, command set.
Your modem manual should give details on how to configure it.
Page 98 Milltronics BW500 – INSTRUCTION MANUAL 7ML19985DK03