Dm Jumper; Ch_Gnd Jumper; Unbal_Ref Jumper - Canoga Perkins 2240 User Manual

4.3.4 DM Jumper

The DM jumper controls the behavior of the DM signal. The EIA position turns
DM OFF when the far-end 2240 modem has a local loopback active. The TEST
position causes DM to turn OFF whenever any loopback is active at one or both
modems.
Factory Setting = EIA

4.3.5 CH_GND Jumper

The jumper selects whether chassis ground is connected directly to signal ground
(SHORT position) or through a 100 Ohm resistor (100_OHM position).
NOTE: In the standalone model, the 100_OHM position will only
put a 100 Ohm resistor between the two grounds if the 2240's main
board SIGNAL GND jumper is set to the FLOAT position.
When installed in the 2201 Rack Chassis, any modem main board,
interface or rack chassis jumper being set to SHORT will override
the FLOAT and 100_OHM positions on all of the other modems.
CONSIDER THIS JUMPER CAREFULLY.
Factory Setting = 100_OHM

4.3.6 UNBAL_REF Jumper

RS-449 specifies that unbalanced inputs to a DCE are to be referenced to the SC
(Send Common) pin. This pin on the DCE is tied to the signal ground of the DTE
through the interface cable. If this ground connection is present, and you prefer to
use it, move the UNBAL_REF jumpers to SC.
Factory Setting = GND
2240 Fiber Optic Modem
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