Introduction

Abstract

“So near ... as if you were there!” “Excellent speech quality in the high—quality net” “You can now make phone calls where the quality is as good as in usual wireline networks.” “The GSM 1800 standard provides speech transmission with exceptional clarity and brilliance.” These extracts from German telecommunication provider advertisements are some examples showing that quality has become an important marketing factor in telephony. Apart from the terminal equipment and service novelties, it is the speech communication quality which has regained a considerable importance. This is astonishing because the latter has been taken for granted for many years, as long as intelligibility was no longer a problem in ordinary wireline telecommunication networks. Though new technologies have been introduced and a steady transition is made towards fully digital circuits, it seems that speech communication quality tended to decrease again in the mid—term.