Campbell Scientific SC932C Interface - Manual (Page 5)

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SC932C 9-PIN TO RS232-DCE INTERFACE
The SC932C is used to interface a Campbell Scientific datalogger to modem devices that are configured
with an RS232 DCE (Data Communications Equipment) serial port. The most common application is to
allow the connection of a RAD short haul modem or third party telephone modem to a datalogger.
The SC932C has the following features:
• Generates true RS232 signal levels to the DCE device, resulting in good noise immunity.
• Powered from the 5V supply of the datalogger, which is also available to provide power to the DCE,
if required for line-powered modems.
• Generates the required ring signal to wake up the datalogger, either when characters are received
or when there is a ring signal from the DCE.
• Allows simultaneous connection of synchronous devices (e.g., Storage Modules) to the datalogger.
• Provides a mechanism for the datalogger to control the line state of intelligent modems via DTR
handshaking control.
• Convenient ‘jumperless’ design.
1. INSTALLATION
Use the SC12 ribbon cable (provided) to
connect the datalogger’s 9-pin CS I/O port to
the 9-pin connector on the SC932C. The
SC932C can usually be connected to the
RS232 device by plugging the SC932C directly
into the serial connector on the RS232 device.
No further configuration is normally required.
A typical application with a RAD modem would
comprise:
SC932C
FIGURE 1. SC932C Connected to RAD
Short-Haul Modem
If the RS232 device does not have a suitable
25-pin ‘D’ socket, you may need an adaptor
cable (see Appendix A).
2. USE WITH INTELLIGENT
TELEPHONE MODEMS
If an ‘intelligent’ telephone modem is being
used, configure it to allow the SC932C to
control its line status via the DTR line. This can
prevent the modem staying on-line
unnecessarily, which can lead to excessive
telephone charges and also delay reconnection
to the datalogger.
Most phone modems can be configured to
respond to the DTR line, although this is not
always the default setting. Although this feature
is sometimes controlled by a hardware
configuration switch, more often it is a software
setting, e.g. AT&D2&W is the command for a
Hayes-compatible modem to force the modem
to follow the DTR status.
3. OTHER APPLICATIONS
The SC932C can be used in more specialized
applications. Appendix B gives installation
details where even lower power consumption
may be possible, and also for applications
where higher power outputs for the RS232
device are required.