Holtgreven GSE-375 - Manual (Page 16)

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3. Remove U4 and the white jumper from the socket of the main board.
4. Snap in the plastic spacers into the three mounting holes surrounding the U4 socket.
Refer to Figure 2-1.
5. Gently press the option board into the socket and make sure the board snaps onto the
standoffs.
6. Reinstall the enclosure bottom plate.
BI-Directional
Both the transmit output and the receive input of the Model 370/375 are available as 20 mA
signals. None of the handshake signals are supported for the 20-mA current loop operation.
Baud
Only baud rates of 9600 baud and less are supported.
Active/Passive
The Tx output may be used as an active or passive output from the Model 370/375. Either active
or passive is chosen depending upon which terminals are used for the connections. In active
mode the Model 370/375 supplies the current. In passive mode, the external device supplies the
current. The Rx input is available in passive mode only.
Isolation
The input and output are electrically isolated from the main board as well as earth ground and
each other, for both passive and active modes of operation. Isolation is a minimum of 1000v.
Max Voltage
Active mode Tx current loop provides a driving voltage of 12v. This will allow 20 mA current flow
with up to a 600 ohm load. Passive mode will work with an external driving voltage of up to 50v.
Connections
The field connections to the 20 mA circuitry will be made at the 9 pin 'D' connector on the rear of
the Model 370/375.
Transmit Current Input Active = TA
Transmit Current Input Passive = TP
Transmit Output = TXO
Receive Current Input = RXI
Receive Current Output = RX
Cable
The length for the current loop is 1000 ft. maximum. This is for the entire loop, not from device to
device. Example: 1 transmitter and 1 receiver can have a maximum of 500 ft. of 2 conductor
cable between them.
Comm port 1 pin out Connection
1 No connection
2 RX IN
3 RX Pass
4 VCC
5 TX
Active
6 Ground
7 TX
OUT
8 TX Pass
9 VCC