Synchronising voiceband modems

Modern voiceband modems often use a symbol rate that is not a factor of their data rate. Combined with the possible use of multidimensional trellis-coded modulation, this means that modems must transmit a fractional number of bits per symbol. To allow for this, bits must be mapped in blocks of symbols. This raises the issue of how to synchronise these blocks. The author gives a fast and reliable means to do this.