CANOGA PERKINS 2240 Fiber Optic Modem - Manual (Page 57)

Chapter 4 Data Interfaces
Multi-Channel Interfaces
57
interface signal inputs which can be used to activate the LOC or REM loop functions. These
signals can control the loopback functions only if the front panel switch is in the center or OFF
position.
4.6.3 RS_BIAS Jumper
The RS_BIAS jumper controls the state that RS floats to when there is no signal driving the RS
pin. The OFF position forces this signal to the OFF (negated) state when the interface cable is
disconnected. The ON position forces it to ON (asserted).
Factory setting: OFF
4.6.4 RR Jumper
The RR jumper determines the source of the RR output. In the CTRL position, the RR output
functions as the output for the RS input at the far end. In the CD jumper position, the RR output
will turn ON either when the modem's fiber optic receiver is in sync (main PCBA internal switch
S1 CD/DCD = OFF and CD/SYNC = ON) or when the far end RTS is ON (main PCBA 8internal
switch S1 CD/DCD = ON and CD/SYNC = OFF). Refer to section 2.1.3.1 for more information on
the internal switch S1 CD/DCD and CD/SYNC positions.
Factory setting: CTRL
4.6.5 CS_GATE Jumper
The CS_GATE jumper controls the state of CS when the local RS is ON. When the jumper is in
the ON position, CTS follows RS only. The CD position allows the 2240's standard data interface
signal CD to gate CS. In the CD jumper position and with local RS ON, CS will turn ON either
when the modem's fiber optic receiver is in sync (main board internal switch S1 CD/DCD = OFF
and CD/SYNC = ON) or the RTS signal at the far end is ON (main board internal switch S1 CD/
DCD = ON and CD/SYNC = OFF). Refer to section 2.1.3.1 for more information on the internal
switch S1 CD/DCD and CD/SYNC positions.
Factory setting: ON
4.6.6 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
4.6.7 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