Reduced complexity signal transmission system

In a CELP coder, a comparison between a target signal and a plurality of synthetic signals is made. The synthetic signal is derived by filtering a plurality of excitation sequences by a synthesis filter having parameters derived from the target signal. The excitation signal which results in a minimum error between the target signal and synthetic signal is selected. The search for the best excitation signal requires a substantial computational complexity. To reduce the complexity, a preselection of a small number of excitation sequences is made using a reduced complexity synthesis filter. With this small number of excitation sequences, a full complexity search is made. Due to the reduced number of excitation sequences involved in the final selection, the required computational complexity is reduced.