The complete ASTi system is too extensive to cover within the confines of a brief application note. Instead, this note will focus on ASTi's communications system, which solved some especially difficult problems.

The key communications problems were:

1. How do you give a large number of physically disperse operators access to a bank of simulated on-board and off-board radio transceivers, navigation receivers and multiple intercom buses?
2. Network Traffic Management. How do you effectively and economically constrain intercom traffic to the local network, while simultaneously allowing radio communications traffic over the wide area network?

A summary of the communications requirements illustrates the magnitude of the problem:

• Operators (spanning thousands of feet of cable runs):
  • On-board: Pilot, Copilot, Navigator, Electronic Warfare Officer (EWO), Fire Control Officer (FCO), Flight Engineer (FE), All Light Level TV Operator (ALLTV) and Infrared Detection Set Operator (IDR)
  • (32) Off-board: Instructors, Observers, Stealth Positions, MODSAF Positions, Auxiliary Audio Feeds and Spare / Future Expansion
• Radio Communications:
  • On-board: VHF 1, VHF 2, UHF 1, UHF 2, HF 1, HF 2 and SATCOM
  • Off-board: VHF A VHF B, UHF A, UHF B, HF A, HF B and SATCOM A
  • High fidelity radio propagation effects and crypto effects (KY-58 / KYV-5)
• Navigation:
  • On-board Receivers: TACAN 1, TACAN 2, VOR 1, VOR 2, IFF and ADF
  • Off-board Transmitters: TACAN A, TACAN B, VOR A, VOR B, IFF A and ADF A
• Intercoms:
  • (14) Busses, including: Main, (2) Private, INET, Emergency, (5) Local, (4) ISO

The problem can be simply described as a large communications matrix, defined by two axes: 40 Distributed Operator Interfaces by 29 Communications Nets. A portion of the AC-130U communications matrix is shown in Figure 2. This paper will examine the ASTi communications system by way of a series of examples related to this matrix.