[sdiy] [SDIY] First switgh detector

[Dave Kendall]

Bill - you could try the CMOS 4532 priority encoder....

cheers,
Dave

On May 20, 2011, at 04:25, bill bigrig wrote:

> Howdy,
>
>  On tha V-tech talking tablet, there is a bend out there that uses 2 
> rotary switches to select the letter/number button being "pushed", 
> i.e. the one to mangle). Is there a way, other than cascading a bunch 
> if XOR gates to give real time control of which button is being 
> pushed? There is no FSK or such, just a 6x7 matrix. One button rotary 
> switch for one, one for the other. Is there not a Cmos way to detect 
> the first button pushed and ignore all others until that buttton is 
> released? I'd like to work with the circuit bends without having to 
> pre-select the digit with switches, but, push any button and have the 
> 'Glitch" work on the button that is currently being held down. Thanx.
> Rig
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