[time-nuts] interesting HP divider and clock on ebay

[Tom Van Baak]

> If the 115 has no motor (and I'm not questioning you, Bill) what moves the
> "digital" numbers? It looks like a clock drive, and the 1968 HP catalog
> makes reference to an "additional drum," which also sounds like a motor
> drive.
> 
> Jeremy

The 115 does have a motor; the digital readout works like an odometer.
Here's four of many photos of a 115BR and 115CR:

exterior:
http://www.dvq.com/oldcomp/hp/large/hp_115br_1.JPG
http://www.dvq.com/oldcomp/hp/large/hp115cr_1.JPG

interior:
http://www.dvq.com/oldcomp/hp/large/hp_115br_2.JPG
http://www.dvq.com/oldcomp/hp/large/hp_115br_5.JPG
http://www.dvq.com/oldcomp/hp/large/hp115cr_4.JPG

The last photo (hp115cr_4.JPG) is particularly nice.

Note also the NNN.NNN millisecond advance/retard feature. This is done with an analog phase resolver and digital turn counter.

/tvb