Specifications

Schneider Electric

Interfaces (continued)

Modems

Bits cannot be transmitted directly over a telephone line (except for an ISDN line). A

telephone conversation between two people is analogue because it varies in

amplitude and phase over time.

Transmission of the bits 1 and 0 corresponds to variations in continuous voltage and

thus cannot be placed directly on the telephone line. Modems are used to "MOdulate

and DEModulate" these bits into analogue signals.

There are four types of modulation:

Definition: a modem, or MOdulator DEModulator is a device used to change digital

signals into analogue signals and vice-versa.

b Amplitude modulation

b Frequency modulation

b Phase modulation (synchronisation)

b Combined modulation (ex.: of amplitude and phase)

For long-distance communication, the

easiest solution is to use the existing

telephone network. This requires a

MODEM.

E52341E52342E52343E52488

Guide to Integration

Modbus / Jbus