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Old 4th Apr 2018, 5:57 pm   #20
TonyDuell
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Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,188
Default Re: HP 5245L counter crystal oscillator

Quote:
Originally Posted by cmjones01 View Post
Yes, it's amazing. The binary (or is it biquinary? Or something else?) encoding of the counter is decoded to decimal for the nixie tubes using an array of neon bulbs and photocells deposited on a ceramic substrate. Incredibly ingenious.
I seem to remember that the standard version is 1242 BCD (that is, 4 bits with weights of 1, 2, 4, 2, so that 1111 = 9). I think there was an option to have normal 1248 BCD code. I do have the service manual, but it's upstairs...

Talking of Biquinary (and going off-topic for a moment, sorry), somewhere I have a Philips (who else!) counter with what could be classed as biquinary nixie tubes. These devices have 5 cathode pins and 2 anodes (and probably screens too). The cathodes shapped for 0 and 1 share a pin, ditto 2 and 3, etc. But they are associated with different anodes. So the anode is selected by the LSB of the counter, the other bits select one of 5 pairs of cathodes.
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