The Field Comm Support Unit is an administrative vehicle used by a Field Comm dispatcher/supervisor. It was used in field technical tests in Manhattan for a short time last year, but is not normally an emergency response vehicle.
The Field Comm Satellite engines each carry two sound-powered phones and two 500-foot cable reels. Magnets are not involved (could you be thinking of the earlier Figaro HF radio systems which the sound- powered phones replaced?). Additional sound-powered phones and reels are carried by the high-rise units, rescue companies, and some battalions.