Campbell Scientific SC932 9-Pin to RS-232-DCE Interface - Manual (Page 11)

SC932 9-Pin to RS-232-DCE Interface
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4. RAD Modem Application
The SC932 is most frequently used with a short range modem to communicate
across a 4-wire, unconditioned dedicated line. This section describes the
details of this application using a short range asynchronous modem built by
RAD*.
* SRM - 5A RAD Modem
RAD Data Communications Inc.
900 Corporate Drive
Mahwah, NJ 07430
Tel: (201) 529-1100
Fax: (201) 529-5777
Email: [email protected]
http://www.rad.com
For transmission, the RAD modem uses a cable made of 2 pairs of twisted
wires with a shield. Data rates up to 9600 bps are possible. The low voltage
transmission levels minimize cross-talk between adjacent lines within the same
cable. Data are transmitted and received at a balanced impedance, providing
excellent immunity to circuit noise. Table 1 gives the data rate possible for
several gage cables across several distances.
TABLE 1. Approximate Range, miles and km
Data Rate 19 Gauge (0.9 mm) 24 Gauge (0.5 mm) 26 Gauge (0.4 mm)
bps miles km miles km miles km
9,600 6.2 10.0 2.8 4.5 2.0 3.3
1,200 7.6 12.2 3.4 5.5 2.5 4.0
Figures 4, 5, and 6 show specific jumper settings for three applications with the
RAD Modem. Figure 4 is an example of two way communication with a
computer, Figure 5 shows one way communication to a printer or display, and
Figure 6 shows both. Note the differences in jumper settings.
4.1 RAD Modem - Two Way
FIGURE 4. Two Way Communication