The following table shows the factory default settings of switches
S1 and S3. Following the table are descriptions of each switch.
Switches S1 and S3: Transmitter Active/Passive Select
Slide switches S1 (TXA) and S3 (TXB) are used to set the port A
and port B transmitter modes of operation, respectively. When the
active mode of operation is selected, the Model 2017RC transmitter will
supply the 20mA loop current to the connected passive receiver. When
the passive mode of operation is selected, the Model 2017RC
transmitter must be connected to an active receiver.
5
DCE
DTE
ACTIVE PASSIVE
TX
SWITCH SUMMARY TABLE
Position
Function
Factory Default
S1
Transmitter (A) Mode Select
Active
S3
Transmitter (B) Mode Select
Active
Figure 2.
Orientation of transmitter active/passive switch
PORT A
3.1.2 Setting the Receiver Impedance Straps
JB1 and JB2 are used to set the input impedance of the port A and
port B receivers, respectively. This allows the user to choose the
optimum impedance setting for the particular application. There are
two possible positions for JB1 and JB2: strap covering posts 1 & 2, or
strap covering posts 2 & 3. Figure 3 shows the orientation of the strap
with respect to its post positions.
The following table provides a summary of strap functions rear
interface card.
Straps JB1 and JB2: Receiver Impedance
In the normal setting, JB1 and JB2 are positioned on posts 1 and
2. The “Normal” setting is best suited for applications in which two
Model 2017RCs are used together. The low impedance setting may
improve performance with other current loop devices.
JB1
Position 1&2 = Normal
(default)
Position 2&3 = Low Receiver Impedance
JB2
Position 1&2 = Normal
(default)
Position 2&3 = Low Receiver Impedance
NOTE:
peg 1 is oriented toward top of card, peg 3 is oriented toward bottom of card
6
Strap
Position 1&2
Position 2&3
JB1
Normal
†
Low
JB2
Normal
†
Low
IMPEDANCE STRAP SUMMARY TABLE
NOTE:
†
indicates factory default
1
2
3
1
2
3
1
2
3
Figure 3.
Orientation of interface card straps
