That's one of the several schemes that were used in RS-232 based polling systems. I remember the "Uniscope" protocol (Sperry Univac) that allowed a terminal to raise its "Request to Send" line when its address, composed of a remote id, site id, device id ("rid,sid,did") was received by it. The host would acknowledge the request with a "Clear to Send" signal and the terminal would send its screenfull of data to the communications controller. We're talking late 70's here...