User's Guide _______________________________________________________________________ 
60  ___________________________________________________________________ M211107EN-C 
Modem DXL421 (Optional) 
The DXL421 modem is a leased line modem module compliant with 
V.21, 300/300 bps FSK, V.22 1200/1200 DPSK, and V.23 1200/1200 
bps FSK. It is applicable to long distance communications (~10 km) 
using a leased telephone grade cable. It should not be used in public 
telephone networks because that requires certain approvals by the service 
provider. However, most of the commercial modems that comply with 
the CCITT standards, as well as the DMX50 and DMX55 modems for 
the Vaisala MILOS 500, can be used with the DXL421 modem. 
If the modem is installed (the unit was ordered with the modem option), 
connect the incoming signal wires to the DLX421 modem line screw 
terminals 3 and 4. See Figure 33 below. 
NOTE 
The DXL421 modem replaces the DMX501 modem. The DMX501 
modem is no longer available but it can still be used with FS11. 
Replacing the modem does not cause any changes to the data 
transmission through modem, except that v.22 bis is no longer supported. 
The FS11 serial commands for configuring the modem settings only 
work with the DMX501 modem. 
 
NOTE 
The cable shield of the modem cable must be properly grounded in the 
cable gland of
 the interface unit's enclosure; see Figure 29 on page 56. 
 
 
  1303-065 
Figure 33  DXL421 Modem Wiring 
If the DXL421 modem is not installed, it can also be retrofitted to the 
FSI102 interface unit. To do this turn the AC (mains) power switch (also 
the battery backup switch if installed) off.