I've handled speechless a/c a few times, and I will add further detail in the morning.
When it's happened to me, I've said "Are you familiar with the speechless code: Click ONCE for yes, TWICE for no, THREE for say again"... and go on from there.
Four clicks is something I've only experienced from the military which announces "I AM SPEECHLESS". There is a further checklist to carry on using the aforementioned format.
To announce a further emergency, the morse code for "X" is sometimes used in the civvy world, but is always taught in the mil. There are not a great many radio operators ( from AG up) who recognise this. I myself was once "caught out" by it.
Hope this is of some help.
Foxy