0x13 Physical Span

Byte | AIB Field Description
--- | ---
2 | Address Element 0x13
3 | Data Length 0x02
4 | Data[0] Slot Number (0x00–0x0F)
5 | Data[1] Physical Span NOTE: When you use this AIB for Loop Timing on the EXNET-ONE or EXNET Connect® card, this field represents the span offset number of the span to be the loop timing source. To derive timing from the EXNET® ring, the Physical Span Number is not used.

See Address Information Block.
The information in an AIB that follows the header, down to the data field. An AIB can have one or more Address Elements. AEs correspond to Span, Channel, and SS7 Link.
Range of channels provided by T1 or E1 transmission service. A physical span is a group of channels taking up a single physical wire. A logical span is a group of channels taking up less than a single logical wire, or carried over more than one physical wire.
Excel's open architecture, proprietary, 1.3 Gbps fiber optic network using a packet-based protocol.