Instruct: Classify a given Amazon review into positive or negative sentiment.
Query: Hummingbird Smartcast RF40_B B-channel does not work with the RF15

Recently bought a Hummingbird Smartcast RF15 (comes with one Channel A remote sonar).In addition I have deliberately purchased a Channel B RF40-B remote sonar.The channel A remote sonar works perfectly.The channel B remote sonar does not work - yes, I do change the channel reception to B on the RF15, but still - no signal