Don't forget B8ZS which did way with the need for SFon copper data T1s
On 1/27/2020 10:43 AM, Lyle Giese wrote:
64k vs 56k was the result of changing T1 framing from SF to ESF. SF
utilized AMI(Alt Mark Inversion) required for copper T1 lines between
Central Offices. SF(Super Frame) robbed bits for signalling and
limited each voice channel to 56k. Conversion to fiber between TELCO
offices allowed the conversion of SF to ESF, which dropped the AMI
requirement and the resultant bit robbing, allowing 64k throughput per
voice channel.
In other words, the limitation was in the inter-office T1's and the
conversion of to fiber between TELCO offices cleared that hurdle.
Lyle Giese
LCR Computer Services, Inc.