27297 Parallax Inc, 27297 Datasheet - Page 127

• Manufacturer Part Number: 27297
• Description: KIT STAMPWORKS WITH BS2-IC
• Manufacturer: Parallax Inc

Specifications of 27297

• Lead Free Status: Contains lead
• Product: Microcontroller Accessories
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Moving Forward · Page 117
Behind the Scenes
With a bit of programming creativity, the BASIC Stamp microcontroller is able to
create and mimic some very interesting sound effects, particularly those used in
telephone system. Since most of the sounds we hear on the telephone (other than
voice) are generated with two tones, the BASIC Stamp’s FREQOUT and DTMFOUT
functions can be used to generate the effects.
DTMFOUT is actually a specialized version of FREQOUT that plays two simultaneous
tones that are superimposed on each other. The purpose of DTMFOUT is to create
the dual-tones required to dial a telephone. The figure below shows the raw and
filtered output of DTMFOUT. In the filtered output the interaction of the two tones is
clearly visible.