Steve Smith wrote:

> Consider using a change over switch which not only disconnects the
> input signal but also shorts the input.

  The trick is to use on a PCB, a multi-pole slide switch with three or
four times the number of changeovers you want.  The critical isolations
are performed by two slides in series with an adjacent slide grounding
the "halfway" connection when it is open.

  "Oak"-style rotaries can also be designed to do this job particularly
well.  Consider a three-position rotary with the middle contact of the
three grounded.  Or a three-position slide likewise.

  I'm not at all sure PIN diodes are better than switch contacts.  Of
switch contacts, slides are likely better, and you want the shortest
pins possible, closest to the PCB.

  If you take a look at the changeover boxes for video games, you will
note the use of a slide with an exceptionally long travel, also guards
including a sliding shield around the actuator.
--
  Cheers,
        Paul B.