a touch sensing apparatus for receiving input from one or more touch stimulating devices employs a spread spectrum signaling arrangement to transmit signals from the touch stimulating devices for identification and location determination . spread spectrum techniques may include dsss , fhss , thss , chirp , or combinations thereof . passive devices operate in the propagation medium of an energy field formed of acoustic , em , or light waves and reflect signals to signal pickups , where rss or time delay techniques are used to determine location and spread spectrum encoding is used to identify the devices . active devices generate a touch stimulating signal that is spread spectrum encoded for identification , and signal pickups in a propagation medium receive the touch stimulation signals which are identified by the ss encoding and located using rss or time - delay techniques .