Throttle flow of samples such that the average rate does not exceed samples_per_sec
This should only be used in GUI apps where there is no other rate limiting block. It is not intended nor effective at precisely controlling the rate of samples. That should be controlled by a source or sink tied to sample clock. E.g., a USRP or audio card.
The Throttle Block is typically attached directly to the output of a source block (e.g. Signal Source).
In this example flowgraph, if you remove the Throttle block the output will look the same, but your CPU will be at 100% and GNU Radio might crash.