rees@apollo.uucp (Jim Rees) (05/26/87)
I have a Zenith Space Commander 200, one of the first wireless TV remote control units ever made (~1960). It has 4 ultrasonic gongs inside, and when you push one of the buttons, it emits a tone in the range 35-50 KHz for a fraction of a second. I want to build a receiver to decode these tones. Any suggestions on what to use as a receiving transducer? I have an ultrasonic microphone of unknown ancestry, but it seems to be too narrow band judging by the scope trace I get out of it. Also, what kind of circuit to decode the tones? I could build four hi-Q tuned circuits out of LC or active filters, but maybe some of you digital hacks could suggest some kind of one-chip discriminator that would do the trick. Maybe a modem chip? I think I could blunder my way through the design if I had some part numbers to look up. I want to retain the remote controller in its original form, so suggestions involving replacing its innards with IR are not useful. (I'm a TV collector, and plan to use this with a 25" GE manufacturing prototype from 1966, in case you're curious).