how to output signal using NI DAQmx continuously

I need to output sinusoidal signal using NI channel

I code like following;

s=daq.createSession('ni'); ch=s.addAnalogOutputChannel('6711',0,'Voltages'); rate=66000; s.Rate=rate; f=3300; t=(1:rate)/rate; output=sin(2*pi*f*t);

s.queueOutputData(output);

lh=addlistener(s,'DataRequired',@queueMoreData);

startBackground(s);

pause(); delete(lh)

// and function queueMoreData is like following

function queueMoreData(src,event) rate=66000; f=3300; t=(1:rate)/rate; output=sin(2*pi*f*t); s.queueOutputData(output); end

and as a result of these code, only one period runs.. I want the sin signal running continuously until I command not to..

What's the problem??