1 INTRODUCTION
The MAS-2 shelf made up of a MAFP module is an asynchronous narrowband modem with
frequency-shift keying (FSK) modulation for the transmission of data at speeds of 50 to
2400 Bd.
The technology used in the MAFP modem is based on digital signal processing and allows
the transmission speed and central frequency of each channel to be programmed by the
user. The transmission speed can be 50, 100, 200, 600, 1200 or 2400 Bd, whilst the central
frequency of each channel can be selected from between a wide range of values, including
those enumerated in recommendations R.35, R.37, R.38A and R.38B of the ITU-T. The
MAFP modem is also compatible with standard V.23 of the ITU-T.
Certain configurations of the MAFP modem allow it to share the available band with speech
frequencies and teleprotection signals. The speech band is limited by a frequency of 300 Hz
and by an upper frequency that is programmable between 2000 and 3400 Hz.
The data interface of the modem complies with specifications V.24 and V.28 of the ITU-T
and RS-232C of EIA.
The modem is equipped with test devices for a rapid operational check. These devices
make it possible to carry out loops and to generate test signals, which allow a DTE to be
emulated for the transmission of the logic levels "1", "0" or "1:0".
1.1 CONSTITUTION OF THE EQUIPMENT
The MAS-2 consists of a shelf that is one standard unit (s.u.) in height and 19” in width.
The MAFP module, incorporated in the shelf, is formed by a single-printed circuit board
where all the elements necessary for the transmission of a succession of binary data in a
voice-frequency channel are located. The main parts of the module are a transmitter block,
a receiver block as well as test and power-supply devices.
