Cool, thanks! No problem. I understand it was analog electronics and using an ultrasonic signal makes sense, but what I wondered about was how did the receiving end (the TV) differentiate between the signals for the different buttons and then decide to execute different procedures based on that. Still pretty interesting in any case.
Speculating, but I would guess they applied a band pass filter to it. You can then either take a simple threshold value, or look for a rapid change and trigger off that. 4 buttons means 4 sets of filters, each tuned to a different frequency.
That said, the analogue electronics engineers of yesteryear were insanely competent and making analogue circuits do interesting things to save money or space.
Cool, thanks! No problem. I understand it was analog electronics and using an ultrasonic signal makes sense, but what I wondered about was how did the receiving end (the TV) differentiate between the signals for the different buttons and then decide to execute different procedures based on that. Still pretty interesting in any case.
Speculating, but I would guess they applied a band pass filter to it. You can then either take a simple threshold value, or look for a rapid change and trigger off that. 4 buttons means 4 sets of filters, each tuned to a different frequency.
That said, the analogue electronics engineers of yesteryear were insanely competent and making analogue circuits do interesting things to save money or space.
Ah, yes, that makes sense, thanks! Totally agreed on those old school engineers being insanely competent and creative.