1. LED Power Meter, Detects RF energy and indicates the result on a multimeter set to 2v or 10v scale. 2. Field Strength Meter MkI. FSM MkI detects RF energy and indicates the result on a multimeter set to 10v scale. 3. Field Strength Meter MkII. FSM MkII has a scale 26MHz to 50MHz. By turning a pointer connected to an air trimmer, the frequency of a transmitter can be determined. 4. Field Strength Meter MkIII - uses a 600 ohm Balance Movement. 5. 27MHz Walkie Talkie - purchase from a toy store.