[CentOS] SysRq over usb serial adapters

I am having trouble sending sysrq commands over USB serial, and I'm
not sure what else to check.

I have two identical machines, each with usb-to-serial adapters,
joined by a null modem adapter.  One runs an agetty, the other
minicom.  I can log in over the agetty as a user and it works as
expected, until I try to send a sysrq.

To send a break in minicom, I type [Ctrl]+[a] then [f].  Then I type
the character [m] to do a test.  I expect to see memory information
print to screen, or at least show up in dmesg.  Instead I only see the
letter m on my shell.

I'm using 115200, 8N1, VT102.  I can echo m > /proc/sysctl-trigger,
and dmesg shows that the sysrq was received when initiated via the
procfs interface.  But not over serial, and that's what I need.
-- 
Billy Crook • Network and Security Administrator • RiskAnalytics, LLC