ADC and V35, RS-232/V24, X21 55

ADCP-50-304 • Issue 19 • June 1999 • Section 4: PatchSwitch X.21

A/B	CHASSIS	BACKPLANE
SWITCHING	CHASSIS	BACKPLANE
MODULE	BACKPLANE	ADAPTER
	SWITCHING
	CIRCUIT
	ALARM
	CIRCUITS
PATCH		X.21
		X.21
A		A
	A	A
	A
	B
B		B
C		C
C
		1633-A

Figure 4-6. A/B Switching Block Diagram

3.2Switch Module Interlocks

The A/B switch activates the A/B relays. The A/B relays complete the X.21 circuit between the DCE and either the DTE-A or DTE-B. The relays also switch in the interlock group. A and B status indicators show the DTE-A and DTE-B selection. Switch Interlocks prevent you from accidentally switching two modules to the same spare or equipment. The A/B interlock jumper Groups 1, 2, 3, and 4 allow for connection of each module to one of four different groups. The A/B interlock Group V allows each module on a chassis to be interlocked vertically with corresponding modules on any chassis connected with an interchassis interlock cable (catalog number 4WC-03).

3.3Monitor, Patch, and Access Modules

These modules contain three front panel jacks for easy access to the X.21 data circuit, and rear connectors for attaching the module to the digital circuit. The rear connectors are provided to interface with the computers communications network. A portion of the rear connector is used to attach the X.21 circuit from the DTE (a computer or front end processor). The remainder of the rear connector is used to attach the circuit to the DCE (a modem).

In the normal mode (no patch cords inserted into the top or middle front jacks), the X.21 circuit has a through-path into and out of the Patch module. In the normal mode, the insertion of a patch cord connector into the top or middle front panel jack allows the entire circuit to be monitored with no interruption of the signals. In the patch mode, insertion of a patch cord connector into the bottom front panel jack breaks the circuit and permits monitoring of only the DCE portion of the data circuit.

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