Timeslot 0 of every basic frame is reserved for basic frame alignment and contains either a Frame Alignment Signal (FAS) or a Non-Frame Alignment Signal (NFAS). FAS and NFAS occur in timeslot0 of consecutive basic frames. Bits four to eight of the NFAS (i.e., Sa4 - Sa8) are additional spare bits generally called as Signaling Associated (Sa) bits.
The HDLC frames can be transmitted on timeslot 0 Sa bits (bits 4-8 of the non-frame alignment signal) and can operate at 4,8,12,16 or 20 kbit/s depending on which Sa bit is selected.
GL's Sa Bits HDLC Analyzer performs Sa Bits HDLC protocol analysis on E1 timeslot 0 during real-time and off-line. Users can capture stream of Sa Bit HDLC frames on the selected even or odd frames of the E1 multiframe on timeslot 0. Captured information can be saved to disk for later off-line analysis. Both real-time and off-line analysis presents summary and detailed views of Sa Bit HDLC decode information. Captured frames can later be used for traffic simulation using the Sa Bits HDLC transmit application.
GL Communications support the following types of Sa Bit HDLC analyzers:
- Real-time Sa Bit HDLC Analyzer (Pre-requisites: GL's field proven E1 or T1 internal cards or Laptop E1 or T1 external units, required licenses and Windows XP (or higher) Operating System)
- Offline Sa Bit HDLC Analyzer (Pre-requisites: Hardware Dongle, and Windows XP (or higher) Operating System)
In addition, the following Sa Bit HDLC applications are supported that further help in transmitting and capturing pre-defined Sa Bit HDLC frames
- Sa Bit HDLC Playback
- Automated Sa Bit HDLC Testing using Client Server
- SSM Analyzer