Vaisala LT31, Руководство пользователя

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Chapter 4 _______________________________________________________________ Installation
VAISALA _______________________________________________________________________ 81
Figure 38 below illustrates an RS-485 application using a half-duplex
data transfer over a single twisted pair.
9502-061
Figure 38 RS-485 Option
Modem DMX501 (optional)
The DMX501 modem is a leased line modem module and it is compliant
with 300 bps V.21, 1200 bps V.22, 2400 bps V.22 bis, and 1200/75 bps
V.23. It is applicable to long distance communications (~10 km) using a
leased telephone grade cable. Since the modem is not approved by the
PTT (Post, Telephone, and Telegraph), it should not be used in public
telephone networks. However, most of the commercial brands following
the CCITT standards, as well as the DMX50 and DMX55 modems for
the Vaisala MILOS500, can be used with the DMX501 modem.
If the modem is installed (LT31 was ordered with the modem option),
connect the incoming signal wires to the MOD3 and MOD4 screw
terminals 25 and 26 at the CPU board LTC212. See Figure 39 on page
82.
NOTE The cable shield of the modem cable must be properly grounded in the
cable gland of the interface enclosure, see Figure 35 on page 77.