Re: [Discuss-gnuradio] GRC squelch block with separate control signal?

[John Ackermann N8UR]

Tom Rondeau said the following on 09/06/2011 11:28 AM:
> On Tue, Sep 6, 2011 at 10:22 AM, John Ackermann N8UR <address@hidden
> <mailto:address@hidden>> wrote:
>
>     I want to implement the equivalent of a carrier-operated relay -- a
>     squelch block that provides an "on" signal at a threshold input
>     signal level, which then passes or blocks data at some point further
>     downstream rather than right at the point where the sensing is
>     happening.
>
>     Are there GRC blocks that will allow this?
>
>     Thanks,
>
>     John
>
>
>
> John,
> Yes, look in "Level Controls," there is a "Simple Squelch," "Standard
> Squelch," and "Power Squelch" as well as a simple "Threshold." You'll
> have to look closer into this blocks to find out how they work.
>
> Tom

Hi Tom --

The challenge is that the three squelch blocks all sense and switch the 
data stream at the same point -- the input signal is passed or not based 
on its level.  What I need instead is to sense the stream at one point, 
and use that information to switch a different data stream.

I could picture two blocks -- one that sets (and updates) a boolean 
variable based on the current signal level, and another that switches a 
separate sample stream based on whether that variable is true or false. 
 Does GRC support message passing between blocks in that fashion?

The practical example is an FM repeater where the transmitted signal is 
turned on only when the received signal level exceeds a threshold.

Thanks,

John