Minimum qualification for a buy signal : Price of BN future should be above the channel at the time of initiating a trade and the Bank Nifty OBV may be inside the channel or above it but not below the channel. Similarly qualification of a sell signal would be BN future should be below the channel at the time of initiating a trade and the BN OBV may be inside the channel or below it but not above it. That is all there is to it. The SL would be the last pivot below the channel in case of buys and the last pivot above the channel in case of sells.