[GreenKeys] IDed by Larry

[Jim Haynes]

The system I remember was called Highway Mobile Radio Telephone Service
and used the low VHF band Motorola and G.E. equipment.  There were
six frequency pairs, I think allocated to six different regions of
the U.S.  Most mobile sets operated in only one region; but I remember
once seeing a set that had a selector switch for all six.  The
telephone numbers were Z followed by one of A through F for the
frequency pair, and then the other five digits were used by the
selector mechanism.