That's not exactly a mobile phone, the "phone" handset in the car has a push to talk button that you'd have to push when you want to talk, just like keying a mi

That's not exactly a mobile phone, the "phone" handset in the car has a push to talk button that you'd have to push when you want to talk, just like keying a microphone, it was single-duplex communication just like a radio. The other end was just a patch between the radio network and telephone network, which was relatively common before cell phones, my dad could make calls from his company two way radio back in the 70's by asking dispatch to route him through to a phone, they'd make the call and tell him what channel to switch to for he call. And of course there was no privacy, anyone on that channel could listen (or talk) to your call.