scope:

This specification covers the construction and inspection of complete and operative lightweight decoder groups. Also covered under this specification are active readouts appropriate for the particular decoder group types and auxiliary functions such as automatic emergency alarm and selected altitude layer operation.

The decoder group shall accept IFF MK XII (SIF) video signals from the interrogator and decode the signals either passively or actively or both simultaneously. Passive decoding shall include both bracket and SIF codes. Active readout shall be accomplished on an SIF signal (including altitude signal) appearing within a range/azimuth gate on an associated indicator (PPI), and the active readout portion of the equipment shall display the SIF code numbers of the signal and also display the altitude decoded signal.

Enabling signals for active decoding will be initiated by a modification within the indicator (PPI), and the resulting area gate shall be displayed on this indicator (see 3.6.6.1.10).

Video signals supplied by the interrogator set shall, by plug-in arrangement, be accepted in tagged video (see 3.4.15.10) form or in conventionally separated form. This function shall be accomplished by including the necessary control circuitry for separated video and tagged video on a common signal circuit card. Selection of the mode of operation shall be accomplished by simple reversal of insertion of this card or other method as approved by the command or agency concerned. Identification markings shall be provided to show directly the selected mode of operation.

Provisions shall be included in the active decoder to accept and process a range azimuth readout gate from the Navy Tactical Data System (NTDS). Provisions to fulfill this requirement shall consist of inserting into the circuitry one or more plug-in cards supplied with the equipment and stored within the decoder unit. For gate characteristics (see 3.6.1.6.4).

intended Use:

This specification is intended for use in the construction and inspection of complete and operative lightweight decoder groups.