Is there a way from serial TTY to get system attention?

[Tuc at T-B-O-H.NET]

Hi,
 
        I have a Soekris 4801 I bought about a year + 1/2 
ago. It runs FreeBSD (5.5) off a CF card with a USB flash 
to help it. It ran great for 10 months, but over the last 
8 months its been "locking up" on me. I put that in quotes 
because I'm not sure if its the OS or the unit. I do see 
POWER on    and the NET light blinking. No ERROR or DISK. 
When I try to serial tty in, I get nothing. 

        Is there any way anyone knows to find out if the
OS has gone south, or the unit is not operating properly.
Is there some sort of key sequence to ask FreeBSD if its
running or to give SOME sort of life or something? My
only access to it is via a serial TTY.
 
                        Thanks, Tuc