Rịba ama amaokwu a dị n'okpuru ma zaa ajụjụ ahụ mgbe e mesịrị n'otu asụsụ ahụ dị ka amaokwu ahụ:  Passage: GSM ejirila ụdị codec dị iche iche iji kpoo ụda 3.1 kHz n'etiti 7 na 13 kbit / s. Na mbido, a na-eji codecs abụọ, aha ya bụ ụdị ọwa data ha kenyere, akpọrọ Half Rate (6.5 kbit / s) na Full Rate (13 kbit / s). Ndị a na-eji usoro dabeere na linear predictive coding (LPC). Na mgbakwunye na ịrụ ọrụ nke ọma na bitrates, ndị a codecs mekwara ka ọ dịkwuo mfe ịmata akụkụ ndị dị mkpa nke ọdịyo, na-ekwe ka oyi akwa ikuku ikuku na-ebute ụzọ ma chebe akụkụ ndị a nke mgbaàmà ahụ. A gbakwunyere GSM n'afọ 1997 site na codec zuru oke (EFR), codec 12.2 kbit / s nke na-eji ọwa zuru oke. N'ikpeazụ, na mmepe nke UMTS, EFR e refactored n'ime a agbanwe-ọnụego codec akpọ AMR-Narrowband, nke bụ elu àgwà na ike megide nnyonye anya mgbe eji na zuru ọnụego ọwa, ma ọ bụ na-erughị siri ike ma ka dịtụ elu àgwà mgbe eji na ezi redio ọnọdụ na ọkara ọnụego ọwa.  Ajụjụ: Olee kbits ole GSM na-eji?
n'agbata afọ 7 na 13