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Audio wearables

I designed the analog to digital and digital to analog converters for WearComp2 from resistive networks (and later, in the early 1980s, by using more expensive Analog Devices chips). In both cases, I designed these with sufficient throughput for radar, voice, and music.

Music synthesis capability was envisioned as a means of providing information (such as light levels, exposure settings, etc.) in the form of sound, but also evolved into a portable self-entertainment system (a predecessor of the SONY Walkman).

Voice digitization and playback capability in WearComp was included for experimental purposes, with the ultimate objective of taking down voicenotes pertaining to exposure information and the like. Unfortunately, the system only had 4k of RAM (later expanded to 48k), so the voice digitization capability was of little real practical use in the field. However, because I built the analog to digital and digital to analog converters as separate units, facilitating the possibility of full-duplex audio, I used this capability for simple voice processing, such as reverberation, and the like. Computer programs and data (and later commercial software including an assembler) were stored on audio cassettes. In 1981, a battery powered audio cassette recorder served as the only non-volatile digital storage medium for the wearable computer system. The cassette drive also proved useful for storage of voicenotes in analog form. (Later an 8 inch floppy drive, followed by a 5.25 inch floppy drive, were incorporated.)

Because of the limited technology of the era, the system was ``hybrid'' (part digital and part analog) in many regards. In addition to the audio cassette recorder (used to record analog voice as well as digital programs and data), the communications channel was also hybrid.

Communications comprised a total of four voice transceiversgif. On the body, was a radio transmitting constantly on one channel, and another radio receiving constantly on a different channel. At the base station, the situation was the same but with the channels reversed.

The modems I constructed, from simple free-running (non coherent) audio frequency oscillators and corresponding filters, operated at a data rate of approximately 45 bits per second. (Another early communication attempt averaged 1500bps but was somewhat unreliable.)

The hybrid communications channel was capable of sending and receiving full-duplex voice (e.g. to talk to an assistant at the base station) or data (e.g. to control the imaging apparatus at the base station). Video capability was also included in the system, but at a much higher frequency (not going through the radio channel that was used for voice and data). Video was an important aspect of the system, as I desired to see what the scene looked like from the perspective of the base station.

next up previous
Next: The aremac Up: The author's `personal imaging' Previous: Situational awareness

Steve Mann
Tue Jan 6 23:24:56 EST 1998