This is the Cadillac of miniature; concealable FM transmitters; and wireless mikes . Transmits in the standard FM radio band; tune to open frequency. Varactor tuning results in stable signal; free from stray capacitance and drifting. Sensitive; picks up conversations from several feet. Powerful operation on a nine volt battery but could use 12V DC if you are going for distance. Easy to build; good for teaching beginners with just a bit of supervision.