SYS_ALERT(1P)                                       SYS_ALERT(1P)


NAME
       sys_alert - Turns on the flashing light

SYNOPSIS
       sys_alert seconds [-h hostname] [-d device] [-quiet]


DESCRIPTION
       sys_alert activates the Heavenly Shining Beacon of Hope,
       which is currently located over in Portage next to
       Lawrence's machine.

       sys_alert requires a single argument, which is the number
       of seconds of Hope you require.  This can be a fractional
       value.

       It is recommended that the Heavenly Shining Beacon of Hope
       only be used to combat or create stress.


OPTIONS
       Options to the program are:

       -h hostname
            Specifies which computer the Beacon is plugged into.
            The default computer is defined by pdi_alerthost in
            the PDI host table.

       -d device
            The device that the Beacon is connected to.  By
            default this is /dev/ttyf2, the second serial port.

       -quiet
            Don't display status messages.


NOTES
       The Heavenly Shining Beacon of Hope was purchased at the
       Stanford Linear Accelerator garage sale in October 95.

       The hardware required to connect the Beacon to a
       computer's serial port was put together by Lawrence
       Kesteloot.

       The 120 volt line that drives the lamp is optically
       coupled with the computer.  The computer's serial port
       drives an LED that shines into a photoresistor which in
       turn controls the lamp.  This reduces the risk of shorting
       out the computer and it's also rather studly.

       The Heavenly Shining Beacon of Hope is not a beeper.


HARDWARE

       The hardware is a simple power box provided with 120VAC 
       power, 6VDC, and a serial connection. The 120VAC outlet is 
       switched by the presence of the DTR signal on the serial 
       line. The serial connection is optically isolated from 
       the power voltages. Unfortunately, there is not enough 
       current on the serial line to source a high-brightness
       (35mA) LED, so an amplifier is used to boost the signal. 
       An inverter stage is used to turn the LED on (and the 
       power off) when DTR is low:

         

       The circuit was built on the following printed-circuit board:

          


BUGS
       Only rotates clockwise.


SEE ALSO
       sys_moo(1P)


AUTHORS
       Drew Olbrich  10/95