There are two aural sounds, the horn, and the voice callout "stabilizer motion".
The horn sounds every 0.5° of trim change after the initial 0.5–1°.
"Stabilizer motion" sounds when the autopilot or runaway trim motor make a >2° in 30 seconds.
So your second source is the correct one. See text below from an MD-80 flight manual:
Momentary horn sound ...
CNN's take on the DHS announcement:
Washington (CNN) Physical hacking of airplane electrical systems is a realistic possibility that could bring down aircraft, the Department of Homeland Security warned Tuesday.
The government said researchers at a cybersecurity firm ...
It sounds like just another theoretical scenario.
If that "hacker" wanted to do harm, he could also loosen a few bolts, disrupt the engine timing, plant a bomb, you name it.
Sure, in today's world of aircraft loaded with electronic systems the operators have little knowledge of and trust implicitly, it's quite possible that something that deliberately feeds ...
DO-178C is a means of compliance, so it sets out what you need to do to show you are meeting your required safety levels in your design. It does not give advice on what methods you might use along the way.
I have seen static analysis used as part of the process, often with hardware integration and system testing.
DO-178 tools need to be qualified for DO-...
I know the exact answer, even if 2 years late.
Firstly, Collins makes their own displays.
Secondly, it was a conscious decision during CRJ700 development to remain CRT, solely for the reason that airlines already had spares supplies of the CRT displays for the CRJ200 fleet. Changing to LCD in the 700, 900, and 1000 would require two different spares ...