Spectracom 8183A NETCLOCK Instruction Manual page 105

C. Position identifier: 8 millisecond duration.
D. Reference marker, 1 per second. The reference marker
appears as two consecutive position identifiers. The second
position identifier marks the on-time point for the succeeding
code word.
4. Resolution: 10 milliseconds.
5. Code word structure:
BCD: Word seconds digits begin at index count 1. Binary coded
elements occur between position identifier elements P 0 and
P 5 (7 for seconds, 7 for minutes, 6 for hours, and 10 for
days) until the code word is complete. An index marker
occurs between decimal digits in each group to provide
separation for visual resolution. Least significant digit occurs
first.
CF: IRIG formats reserve a set of elements known as Control
Functions (CF) for the encoding of various control,
identification, or other special purpose functions. IRIG B has
27 Control Functions located between elements 50 and 78.
The FAA IRIG B code uses five of the Control Function
elements to encode satellite lock status and time error flags.
For a description of the status and error flag implementation,
refer to Table A-1 and the paragraphs below.
Element 53 (530 ms) is the time sync status bit. Element 53
is a Binary 1 when the receiver locked to GPS, and a Binary
0 when the receiver is not locked to GPS.
Element 55 (550 ms) is the +/- 1.0 millisecond error flag.
Element 55 is set to Binary 1 when the expected time error is
within +/- 1.0 millisecond, and a Binary 0 during all other
conditions of operation.
Element 56 (560 ms) is the +/- 5.0 millisecond error flag.
Element 56 is set to Binary 1 when the expected time error is
within +/- 5.0 milliseconds. and a Binary 0 during all other
conditions of operation.
Element 57 (570 ms) is the +/- 50 millisecond error flag.
Element 57 is set to Binary 1 when the expected time error is
within +/- 50 milliseconds, and a Binary 0 during all other
conditions of operation.
Element 58 (580 ms) is the +/- 500 millisecond error flag.
Element 58 is set to Binary 1 when the expected time error is
within +/- 500 milliseconds, and a Binary 0 during all other
conditions of operation.
NetClock/GTP Instruction Manual
Appendix A: FAA IRIG Code Description
Page A-3