Vaisala FD12P - Manual (Page 52)

User's Guide _______________________________________________________________________
52 ______________________________________________________ M210296en-A
9509-014
Figure 18 RS-485 Communication Option
Modem DMX21
The Modem DMX21 is a CCITT V.21 modem, operating at 300 bps.
Connect the signal wires to MODEM LINE 1 and 2, and screw
terminals 7 and 9 on Interface board 16127FD. See the wiring diagram
in Figure 19 on page 53.
In the multidrop configuration, where several FD12P Weather Sensors
are on the same modem line, the units are differentiated by an ID. Set
a different unit ID to each FD12P with the CONF command. In the
multidrop configuration, only one FD12P modem carrier can be active
at the time. To set the modem carrier under the FD12P software
control, set jumper X2 to position 1-3 in the modem interface board as
shown in Figure 19 on page 53. If the X2 jumper is in position 3-4 and
if the unit ID is not set, FD12P keeps the modem carrier signal on all
the time. Set the FD12P to the polling mode with the AMES 0 2
command. The host system must ask data messages by polling each
FD12P.