On Thu, 21 Oct 2010 14:32:23 +0100 Arthur Chance <free...@qeng-ho.org> wrote:
> On 10/21/10 13:38, RW wrote: > > On Wed, 20 Oct 2010 21:10:28 +0100 > > Arthur Chance<free...@qeng-ho.org> wrote: > > > > > >> 50s) had the experience of programming microcode on a machine by > >> inserting brass slugs for 0s and ferrite slugs for 1s on a pin > >> board. > > > > I wonder why it was brass/ferrite rather than brass/empty or > > ferrite/empty. > > Dredging up physics unused for 30+ years, ferrite is ferromagnetic > and intensifies magnetic fields so a coil of wire with ferrite inside > is a massively bigger inductor then an empty coil. I vaguely remember > that brass is slightly diamagnetic, but could be mistaken. If it is, > then it would have the opposite effect and reduce the inductance, so > you'd get a better difference in signal between brass/ferrite than > air/ferrite. Possibly. I'm wondering if there might be three states, where the third state is writable. > Air/brass would give very small differences in signal, I was thinking in that case it would be open/short circuit. _______________________________________________ firstname.lastname@example.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"