CANOGA PERKINS 2240 Fiber Optic Modem - Manual (Page 64)

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Canoga Perkins
4.6.1.1.4 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).
4.6.1.1.5 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
4.6.1.2 RS-423 / DB-25 Interface
NOTE: The maximum data rate for this interface is 9.6 kbps.
This interface is electrically compatible with EIA RS-423A. It will also operate with
asynchronous RS-232D systems.
This interface uses the physical connector type and pinouts specified in RS-232D (refer to
Table 4-I). The RS-423/232D interface uses a 25-pin, female D-type connector for the
physical connection.
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