The internal jumpers mounted on the Model 2703’s PC board
(labeled LK1 - LK7) are used to configure the 75 ohm or 120 ohm net-
work link parameters. Figure 4 (above) shows the location of the
Model 2703’s jumpers on the internal PC board.
The table below shows the factory default jumper settings.
Following the table are descriptions for each jumper.
NOTE: One combination of jumper settings is required for 75 ohm
operation, and another combination is required for 120 ohm opera-
tion. The Model 2703 is factory configured for 75 ohm operation.)
Jumper LK1: 75 Ohm Transmit Shield-to-Ground Connection
This setting determines whether the shield of the 75 Ohm (coax)
transmit cable is connected to earth ground. This connection must be
made when operating in 75 Ohm (unbalanced) mode. Conversely, this
connection must not be made when operating in 120 Ohm (balanced)
mode.
LK1
Setting
Strap On
75 Ohm TX Shield-to-GND Connection Made
Strap Off
75 Ohm TX Shield-to-GND Connection Broken
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JUMPER SUMMARY TABLE
Jumper
Function
75 ohm 120 ohm Factory Default
LK1
75 Ohm TX Shield to GND
On
Off
On (connect)
LK2
75 Ohm RX Shield to GND Opt.*
Off
Off (disconnect)
LK3
Reserved
Off
Off
Off
LK4
120 Ohm Shield to GND
Off
Opt.
Off (disconnect)
LK5
Configuration Auto-Sense
On
Opt.
On (enabled)
LK6
75 Ohm Input Impedance
On
Off
LK7
75 Ohm Input Impedance
On
Off
}
On (75 Ohm)
*Opt. = optional setting, all others are required for proper operation
Jumper LK2: 75 Ohm Receive Shield-to-Ground Connection
This setting determines whether the shield of the 75 Ohm (coax)
receive cable is connected to earth ground. This connection is optional
when operating in 75 Ohm (unbalanced) mode. This connection must
not be made when operating in 120 Ohm (balanced) mode.
LK2
Setting
Strap On
75 Ohm RX Shield-to-GND Connection Made
Strap Off
75 Ohm RX Shield-to-GND Connection Broken
Jumper LK3: Reserved for Future Use
This strap is reserved for future use and must remain Off.
LK3
Setting
Strap On
Not a Valid Setting
Strap Off
Normal Operation
Jumper LK4: 120 Ohm Shield-to-Ground Connection
This setting determines whether the shield of the 120 Ohm (modu-
lar) cable is connected to earth ground. This connection is optional
when operating in 120 Ohm (balanced) mode. This connection must
not be made when operating in 75 Ohm (unbalanced) mode.
LK4
Setting
Strap On
75 Ohm RX Shield-to-GND Connection Made
Strap Off
75 Ohm RX Shield-to-GND Connection Broken
Jumper LK5: Configuration Auto-Sense
This setting determines whether the host can automatically sense
the configuration of the Applique. The operation of the Applique is not
affected by this jumper setting. Auto-sense should be enabled when
operating in 75 Ohm (unbalanced) mode. Current interface standards
do not list this feature for 120 Ohm (balanced) mode.
LK5
Setting
Strap On
Auto-sense enabled
Strap Off
Auto-sense disabled
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