tone generator:


parts:

U1, U1	NE555 timer IC
R1	1 megohm potentiometer
R2	1 1k resistor
C1	0.001uf ceramic capacitor
C2	0.1uF ceramic capacitor
SPKR1	4 or 8 ohm miniature speaker

all resistors are 5 or 10 percent tolerance, 1/4-watt
all capacitors are 10 percent tolerance,
rated 35 volts or higher

this tone generator can be used to control your robot. you will need to use the tone decoder for this. to widen the range, higher or lower - substitute a higher, or lower valued capacitor for c1. for frequencies about 5khz and 15khz, use a piezoelectric element as the speaker. Use a miniature speaker for frequencies under 5khz, and use an ultrasonic transducer for frequencies over 30khz.