hiiiiiiiii everyone i am working on a transmitter & receiver circuit for infra red transmission,,,,,,,,i had worked already on UM91214b but no result,,,,,,,,,currently working on ic XR2206 & XR2211 (fsk modulator & demodulator )for tramsmitting 40 khz & 50 khz,anyone here can suggest some of the circuits for above ic (fsk) or any other ic for tx& rx...........