Vaisala FD12P - Manual (Page 53)

Chapter 3 ________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 53
9509-012
Figure 19 Wiring the Modem
Usually, the modem of the FD12P operates in the answer mode, and
the modem of the host computer in the originate mode. In the standard
FD12P system, the S3 switch on the DMX21 board is in the DOWN
position and the answer mode is selected. When the switch is in the
UP position, the originate mode is selected. The transit frequencies of
the DMX21 modem are presented in Table 7 below.
Table 7 Transmit Frequencies of the DMX21 Modem Board
Originate Mode Answer Mode
TXD 0 1 0 1
CCITT 1180 980 1850 1650