COMM.EXE 13
pressing <CTRL>Q. If you encounter data transmission
problems, change the volume on the tape recorder and try again.
Cables
There are 2 types of RS-232C devices: DTE (Data Terminal
Equipment) and DCE (Data Communications Equipment). If a DTE
device is connected directly (pin-for-pin) to another DTE device then
communication cannot occur because both devices are sending on
line 2, and receiving on line 3. Similarly, DCE cannot be connected
pin-for-pin to another DCE.
Your computer is probably a DTE device, although there is no
guarantee of this. There are LI-COR instruments of both types:
DTE: LI-6000, LI-6200, LI-6400, LI-1000, LI-1400, LI-1600,
LI-1200S
DCE: LI-1800 & LI-1800UW terminal ports, LAI-2000, LI-3000A,
LI-6252 CO2 Analyzer, LI-6262 CO2/H2O Analyzer
A cable that interchanges pins 2 and 3 (and usually 6 and 20 as well)
so that DCE can talk to DCE, and DTE can talk to DTE, is known as
a null modem. The printer cable that comes with the LI-6200 is a
null modem cable. A flat ribbon cable is not a null modem cable.
GENERAL RULE: IF IT DOESN'T WORK WITHOUT A
NULL MODEM CABLE, TRY IT WITH A NULL MODEM
CABLE.
Some computers (such as IBM AT and COMPAQ) use a 9 pin
connector for the RS-232 port, in which case an adapter cable is
required. Adapter cables that conform to the IBM AT 9 pin RS-232
standard are available from LI-COR, and most computer stores. You
must decide how you want your cable to be configured at the 25 pin
connector end. Below is a list of LI-COR equipment, and how the
25 pin end of the adapter cable should be configured (male/female,
DCE/DTE):
connects directly to such as LI-COR