Idents on VOR+DME if one of them is inop

Peter wrote:
I am just going through some King video FAA IR training material and
it briefly covers this topic.

On a normal intercom one has selectors for "DME" and "NAV" and one
would ident the VOR and the DME separately. However she mentions a
that one can tell if one or the other is inop from the period of the
ident. How does this work?

Is she assuming some sort of mixed-mode intercom where there is just
a
single "ident" selector? In that case, I can see that if the VOR
(only) was inop then the ident would be heard every 30 secs (the DME
ident) but what about if the DME (only) was inop? There would be some
sort of strange periodicity.

The period of the ident (a missing ident every 4 as I recall) indicates
that the DME is not being transmited. Listening to the DME on the audio
panel just tells you that you are receiving the VOR (and will provide
the same audio the VOR does). Its really a test of the instrument's
reception.

-Robert