Q71B
– Quick Start Guide – v1.4 – May 2022
Ph: +64 3 366 3713
Page 3 of 6
Power Supply Connections
The Q71B is designed to operate from a nominal 12V DC supply voltage within the range 8.0 to 15.0V DC.
A supply voltage greater than 15.0V will blow the 500mA fuse inside the Q71B.
A supply voltage less than 8.0V will result in degraded or unreliable performance.
The DATRAN XL4 Plus, XL4 and eXcel (Rev D) RTUs have two RS232 ports - both can use the Q71B for
analogue radio communications.
The significant difference between the two ports, is that the lower RS232 port (RS232-B) on the Q22D has a
+Vsup DC output supply line. The Q71B can be powered via this line, so long as jumper J23 on the Q22D is
in the 1-2 position. RS232-A port on the processor board does not have this supply line, so the Q71B must
be powered through the three terminal power supply connector. The power supply connections are shown on
the top cover
Left Pin
Middle Pin
Right Pin
GND
Power Supply Negative
+12V
Power Supply Positive (8V
– 15V DC)
Not connected
The default installation position of the Q71B is on the lower RS232-B port.
All new RTUs are configured with the correct jumper setting for this.
However, please check this jumper on existing RTUs before using a Q71B.
If using the modem on the RS232-B port, do not apply power from both the
port and the external supply
If the DATRAN RTU is powered from a 24V DC system:
Do not connect the Q71 modem to this 24V DC supply.
Do not connect the Q71 modem to the RS232-B port. Use RS232-A and the
Radios 12V DC supply connected to the Q71 power connector.
