Black Box ME260A, Owner'S Manual

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23
CHAPTER 2: Introduction
2.3.5 M
ODEM
-E
LIMINATOR
A
PPLICATIONS
In modem-eliminator applications, the Modular Modem Eliminator is used as a
replacement for two synchronous modems to connect two DTEs. The DTEs can
have different interfaces. This mode is used when both sides have general purpose
interfaces (G.703 interface modules include internal clock source).
When using general-purpose interface modules, the distance between the
DTEs and the Modular Modem Eliminator is according to the relevant
interface standard.
General Application Considerations
In a typical application, the Modular Modem Eliminator could be used
to connect communication ports of two hosts (
Figure 2-11 ).
Plug-in interface modules are installed in the Modular Modem Eliminator to
match the interface used by each DTE. Since the Modular Modem Eliminator
emulates modems on both sides, the mode switches on the two interface modules
must be always set to the DCE position. To permit half-duplex operation, the
Modular Modem Eliminator has two carrier-control jumpers, designated
CARRIER-1 and CARRIER-2. Each jumper controls the state of the DCD line
in the corresponding interface:
• For full-duplex operation, the DCD lines must be always active (on).
This corresponds to the ON position of the jumpers.
• For half-duplex operation, the DCD line on one interface must follow the
state of the RTS line on the other interface. This corresponds to the CNTRL
position of the jumpers.
In addition, it is possible to introduce a delay between the activation of the RTS
line of one interface and the activation of the CTS line of the same interface. The
delay is determined by an additional pair of jumpers, DELAY-1 and DELAY-2 (one
for each interface). The available delay settings are 0, 6, and 51 msec.
Figure 2-11. Typical modem-eliminator application.
PCU
PCU
ME260A
56 kbps
56 kbps
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