14
September
2004
TIM1-A2-GZ40-00
Clock Source
Clock source refers to the timing origination for T1 transmission links.
Local (default in provider mode) – Timing is derived from an oscillator on
board the TIM1500.
Loop (default in subscriber mode) – Timing is derives from an intermediate
device on the T1 line.
NOTE: Local timing is the default for a TIM1500 in T1 provider mode. Default for a
TIM1500 in subscriber mode is Loop and cannot be modified.
Frame Type
Frame type is the T1 data encapsulation method. A frame consists of 193 bits
(8-bit samples of each of the 24 T1 data channels plus a synchronization bit)
transmitted at a rate of 8,000 frames per second (1,536 kbps) across the T1 line.
Extended Super Frame (default) – Used in Wide Area Networks (WANs),
Extended Super Frame (ESF) assembles data into 24-frame transmission
clusters and integrates the following:
— Facilities Data Link (FDR): in-service monitoring and diagnostics
— Cyclic Redundancy Check (CRC): scrutinization of data integrity and
detection of line errors
Super Frame – Super Frame (SF) assembles data into 12-frame transmission
clusters.
Line Code
Line code is the T1 mode of transmission. The two line code options for the
TIM1500 both fall within the International Telecommunication Union -
Telecommunication Standardization Sector (ITU-T) G.703 Standards for
Transmission Facilities.
Bipolar with 8 Zero Substitution (default) – Bipolar with 8 Zero Substitution (B8ZS)
line encoding uses bipolar violations to guarantee the presence of pulses in the T1
line thereby helping to prevent loss of synchronization between the TIM1500 and
remote T1 equipment. B8ZS accommodates the minimum ones density
requirement in the North American public network.
Alternate Mark Inversion – Alternate Mark Inversion (AMI) alternates positive and
negative pulses across the T1 line. Although AMI links typically encounter long
strings of zeros which can potentially cause loss of synchronization between T1
units, the TIM1500 meets the North American minimum ones density requirement
internally such that loss of synchronization is prevented between the TIM1500 and
remote T1 equipment with AMI just as it is with B8ZS.
