relay-operators-that-switch

WHY DO TTY RELAY OPERATORS SWITCH IN MIDSTREAM?
The deaf people using the TTY relay have long been accustomed to
switch of TTY relay operators in middle of a TTY relay call. It
could be a concern when a relief operator jumps in cold and has to
learn in a hurry what the call is all about.
Why do they switch? Something to do with union rules? The
Communication Workers of America has a rule limiting the time the
operator can spend in a given work period.