US Robotics COURIER User Manual page 114

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COURIER HIGH SPEED MODEMS
Minimum Requirements
Some computer
I
terminal equipment supports only a few of the
RS-232 signal functions set in the Courier. The minimum
required for the modem to operate are as follows:
Asynchronous Calls
DB-25 DB-9
Pin
2
3
7
20
Pin
3
2
5
4
Function
Transmitted Data
Received Data
Signal Ground
Data Terminal Ready*
*Required only if you have the Data Terminal Ready Override
switch OFF (DIP switch 1 OFF).
Synchronous Calls
You will need all of the above functions as well as pin 15 for
Transmitter timing signals, and pin 17 for Receiver timing
signals. You may need pin 24, which is assigned the external
timing source, rather than the internal (modem) source assigned
to pin 15. See Chapter 7 for more detailed information.
Additional Flow Control Functions
If your computer and software support Clear to Send and you
wish to use Transmit Data hardware flow control (&Hl), Pin 5
(DB-25) or Pin 8 (DB-9) is required.
If your computer and software support Request to Send and you
wish to use Received Data hardware flow control (&R2), Pin 4
(DB-25) or Pin 7 (DB-9) is required.
FOR 38.4K DTE RATE OR HIGHER
Your terminal or computer and software must support the 38.4K
rate. Make sure the RS-232 cable is shielded. Cables are
normally six feet long, but longer lengths are possible. If you
encounter problems with signal degradation, try a shorter cable.
If you decide to build your own cable, use a low-capacitance
cable. To further minimize the capacitance, connect only those
functions (pins) that your application requires.
Summaries and Tables
8-3