From Kodakl1.ftn, I discovered the following serial commands
can be sent to the control computer (PDP) for processing:

R = light is released 
L = waiting for light
0-9 and A-F = set filter wheel position
K = KDP position A
k = KDP position B
Z = KDP neutral
H = Zeiss filter control

---
In KodakMain.c, I found:
R and L

and routines:
ReadFromSerial
WriteToSerial
CheckForLight
DoLBCCommand

which all deal with serial communication.

It looks like the Mac only ever sends:
L
R

but it receives a 28byte string with the following character
values: (see DoLBCCommand)

0-3 RA of telescope in arc seconds from solar disk center
4 RA direction of telescope (E,W)
5-8 Dec of telescope  in arc seconds from solar disk center
9 Dec direction of Telescope (N,S)
10-11 bench code (bench-1? see line 1248)
12-19 filter name (determines obs_type, ie. 'C' of 'F')
20-27 wavelength - unused

Until we have filter control included in telcon and lbc, the
filter name, wavelength, and hence obs_type are currently
wrong.

There is no acknowledgement of the R. It is sent then fairly
soon thereafter, CCDMAC sends L as it waits for its turn to get
the light again.

---
From kodakl1.ftn
It looks like PDP sends the 28byte string to the Mac when 
it gets the L command from the mac and it has moved the light
there. It is basically a "light is there" signal.

---

In testing on the mac, I found I need 9600 Baud and 8N1.
Handshaking? To talk to the WYSE terminal, Ingrid needed
a null modem; to talk to the Mac, she didn't.  Had to change the
Mac code from sending a \r at the end of each command to a \n.

-------
The Vaxes (OSLVax and VMGVax) have a similar (and lengthier) set of
commands.  Currently, I respond to only the following:

IFR - This is an information request - respond with
      IFOttttxxxxyyyyrrrr where tttt is the telescope (0026 or 0010),
                                xxxx is ra, 
                                yyyy is dec, and
                                rrrr is region number.
WAI - Ready for Light
SET - Ready for Light - these two are actually different, but the respone
                        from the software is the same, so they are treated
                        as identical.
EVM - Done with Light
LBR - Done with Light - these two are actually different. EVM means it's ok
                        to move the telescope; LBR means it's not (ex. it's
                        in the middle of a long VMG integration.)
END - exiting seqence - When I get this, I stop cycling, although I don't
                        see it unless Cycling is running at the time the
                        END exiting is sent.  I will see it the next time
                        that camera comes up in the sequence, at which time
                        I stop cycling.

I don't yet deal with STO and should probably arrange it so I see it and
END even when we have already stopped cycling.

For the observing software to have access to the serial ports on the VAX
the following command must be entered from the system account:
  SET PROT=(w:rwlp)/DEV TEL0:
(or placed in the startup file, which it will be eventually...)