scope:

General

The general requirements for interfacing TPWS are given in NR/L2/SIG/10133 (Ref. 1).

Four methods of implementing these requirements for SSI signalling have been adopted, referred to as Methods 1a, 1b, 2, and 3.

The physical interface arrangements for these methods are described in SSI8500D, Section 3.4.

Note that for all methods, the interface with Position Light signals associated with a Main signal (where fitted) will normally be handled in hardware, and the data methods described below are unaffected by the inclusion of such a feature.

The exception to this rule is in complex approaches, where separate control and/or proving of OSS and TSS is employed. Details of the arrangements for complex approaches are described in Section 6.