Introduction

This Recommendation defines the modulation methods and operating sequences for a modem intended only for use in high speed facsimile applications.

Appropriate T-Series Recommendations should be consulted regarding operating procedures and other features employed in facsimile transmission applications, as these differ from those recommended for high speed modems for general applications.

The modem has the following principal characteristics:

a) Provision for half duplex operation at data signalling rates of:

– 14 400 bit/s synchronous,

– 12 000 bit/s synchronous,

– 9600 bit/s synchronous,

– 7200 bit/s synchronous;

b) Quadrature amplitude modulation with synchronous line transmission at 2400 symbols per second.

c) Inclusion of data scramblers, adaptive equalizers and eight-state trellis coding.

d) Two sequences for training and synchronization: long train and resync.