10
NTU-1
3.3 DIP-Switch Options
When you install the NTU-1, you must set the terminating resistors to match the
applications shown in Figure 3-1.
Figure 3-1. Examples using terminating resistor settings.
DIP-switch S1 positions 1 and 4 control the resistors. S1-1 selects the transmit
resistor and S1-4 selects the receive resistor. The ON (down) position puts the
terminating resistors in the circuit. You can access the switch from the rear panel.
It is numbered and labeled (see Figure 3-2). The NTU-1 is shipped with all
positions switched ON (S1 positions 2 and 3 are not used).
100 ohms
IN
Up to 1 km
Up to 1 km
Point-to-Point Connection
Passive Bus
Connection
100 ohms
IN
100 ohms
OUT
NTU-1
Terminal
Eliminator
Terminal
Equipment
Terminal
Equipment
NTU-1
NTU-1
100 ohms OUT
on unit with
shortest cable
100 ohms IN
on unit with
longest cable
If cable length is
equal, 100 ohms IN
on either unit
100 ohms
IN
100 ohms
IN
100 ohms
IN
Example #1
Example #3
Example #2