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CHAPTER 3: Functions

Figure 3-3. Four-Cavity Patching.

When you insert a patch cord into the MON A cavity, it connects to the circuit
between DTE A and the DCE. When you insert a patch cord into the MON B
cavity, it connects to the circuit between DTE B and the DCE. The circuits are not
broken. You can monitor the signals.
When you insert a patch cord into the COMP cavity, the circuit is broken and
the cord is connected to the appropriate DTE. You can test the connected DTE.
When you insert a patch cord into the MODEM cavity, the circuit is broken and
the cord is connected to the DCE. You can test the DCE.
Four-cavity patching is available for use with the following interfaces: RS-232,
V.35, and RS-530.
3.2 Monitoring Bus
The Pro Switching System has two monitoring buses: a digital monitoring bus and
an analog monitoring bus. You can connect a monitoring bus to any line in the
system, allowing monitoring and testing equipment to access that line. When a line
is connected to the monitoring bus, the corresponding card’s MONITOR LED
lights. Figure 3-4 shows a monitoring bus.
Typically, the DTE is connected to the DCE.