Pushbutton dial
I discovered I have a number of brochures for early MTS and IMTS car telephones. One of these features "Pushbutton dial", a proprietary Motorola system pre-dating DTMF and pitched to rural REA co-ops as solving the issue of automatic dialing from mobiles (in order to eliminate a salaried cord-board mobile operator.)
Click on image to enlarge
As far as I know, PB dial was never implemented by any Bell affiliates. It is the same as MTS on land-to-mobile, but mobile to land in the automatic mode involves tone dialing in a strange system where the key stays depressed until the tone duration (preset) has been reached, at which time it pops up to allow you to dial the next digit ! The tones are not DTMF.
It was marketed as a system which prevented mis-dialing because the CO either got the tone or it didn't, unlike a rotary dial where a noise burst could mask one of the pulses and give you a wrong number.
Attached is a photo of the Motorola pushbutton dial control head. The handset hung up separately in this model. The side has a metal tag which says "U.S. AEC" leading me to believe this was used in a private government radiotelephone system in Southern California. Later models, at least in the brochures, show the handset hung up across the face in a cast aluminum cradle. There was also a key lock in that cradle, whereas this one has the lock on the front panel. The photo doesn't really show it, but the panel is actually banked, sloping back on the top edge. Nonetheless, quite ugly compared to the Bell System's MJ control head.
Geoff
Editor's note. The famed industrial designer Henry Dreyfuss styled the MJ control head. No one at Mot could compare to his designs.
