[c-nsp] Cisco 7200 AUX port pseudo-break problem

[Ed Ravin]

On Wed, Aug 24, 2005 at 11:13:36PM -0700, Ted Mittelstaedt wrote:
> 
>   The problem is that a Break signal isn't actually a real character.
> The
> following explains it more throughly with some suggested fixes:
> 
> http://www.cisco.com/warp/public/770/fn-tsbreak.html

I like this suggestion:

  * The "Soldering Iron" solution 
  If you tie a 4.7K resistor (1/4 Watt) between pins 3 and 25 of the ttya
  port, you electrically prevent a BREAK signal either from the key or from
  disconnecting or powering down the terminal. This prevents intentional
  halts except by removing the resistor, but does allow recabling.

This is almost what I want.  I would rather it was remotely switchable,
so I can still send a BREAK when I need to fix problems on the NetBSD
box.  Perhaps a circuit that recognizes two BREAK signals in a row,
like the Hayes modem +++ escape?

Some of the manufacturers of console server equipment know about this
problem and design their hardware so that the signal doesn't "float"
and resemble a break when the console server is turned on or off.  I
was hoping this could be retrofitted into the cable, like the 4.7k
resistor idea above.