three XBees line passing problem


I need to use three XBees in the line passing mode. Two XBees are attached to different sensors serving as transmitters and one XBee serves as a receiver to trigger a motor based on the condition of the two sensors attached to the transmitting XBees. For now, I tried just to attache a force sensor that produces 0V when not pushed and 3 V when pushed to one of the transmitting XBees (the sensor is attached to pin AD4/DIO4). I left the 2nd transmitting XBee free not attached to anything.

I have the connection right and there is an association between the transmitters and receiver. They are connected fine.

Problem: The problem is that when I am measuring the voltage on the AD4/DIO4 pin of the receiver, I see the voltage fluctuating between 0 and 3 constantly when I do not push on the force sensor. When I push on the force sensor, the voltage on the AD4/DIO4 pin of the receiver changes to 3 volts for sometime and again the voltage starts to fluctuate.

Question: How can I configure these two transmitting XBees and one receiving XBee to get stable sensor status from each transmitting XBee?

XBees configuration parameters:

Receiver Transmitters

ATID 1234 1234 ATMY 5678 1234 ATDL 1234 5678 ATAI 0 0 ATIR 14 - ATIT 5 - ATBD 3 3 ATIU 1 - ATIA - 5678 ATD0 3 4 ATD1 3 4 ATD2 3 4 ATD3 3 4 ATD4 3 4 ATD6 3 4

Thank you very much in advance for your feedback and assistance.