Black Box COS-2, Руководство пользователя

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CHAPTER 4: Operation
4.2.3 M
ODEM
(
S
)
↔
COS-2
We do not recommend attaching modems to the High Speed COS-2,
because the COS-2 doesn’t support Pins 4 (RTS) and 22 (RI), and ties
Pins 6 (DSR) and 8 (RLSD [DCD]) high. When other involved devices
(especially PCs running terminal-emulation software) see no signal or only a
constant high signal level on these pins (especially Pins 8 and 22), most
applications involving modems will not function correctly.
However, if the device(s) on the other side of the COS-2 don’t need to see
any of these non-supported or tied-high pins, you can attach one or more
modems to the COS-2, using cables containing at least 5 wires with DB25
male connectors on each end. The cable(s) should be specially “cross-
pinned” as shown in Table 4-3 below. (Our product code for a cable pinned
this way is EYN254C.)
Connect one end of each of these cables to the input port on the selected
modem. If the selected modem is the “source” or “master” (the one that’s doing
the switching), connect the other end of the cable to the COS-2’s port “A.”
If the modem is a “destination” or “slave” (one that’s being switched
between), connect the other end of the cable to the COS-2’s port “B” or “C.”
Some other DCEs—including some multiplexors, line drivers, and short-
haul modems—can function with only Pins 2, 3, 5, 7, and 20. You can
attach them to the COS-2 as described in the previous two paragraphs.
Table 4-3. Pinning, Modem to COS-2*.
Modem COS-2
DB25 DB25
RD 2 ----------------------------------- 3 TD
TD 3 ----------------------------------- 2 RD
CTS† 5 ----------------------------------- 20 DTR†
SGND 7 ----------------------------------- 7 SGND
DTR† 20 ------------------------------------ 5 CTS†
*Our EYN254C cable is pinned this way. It also carries Pin 1, PGND, which the High
Speed COS-2 supports but doesn’t require, as well as Pins 6 and 8 (DSR and RLSD
[DCD] respectively, tied into the CTS
↔
DTR lines), which the COS-2 keeps tied high.
†The COS-2 takes DTR as input from any attached device and passes it through to
the device on the other side as CTS output.