I was an early mobile phone user in California back in the 1970's. There was a special number you could use to call the CHP without charge, not a small thing in those days as otherwise you paid the cost of the mobile call as well as "air time". When the phone companies converted to dial-up mobile phones (IMTS, vs the old MTS), you could then use the 911 to get emergency help or report an accident. However, ZEnith 1-2000 will still get you the CHP in California, toll-free!

With nearly every adult (and many children) having a cell-phone today, can you imagine that at one time there were only 11 radio channels in a city available to the phone companies for mobile phones! And they weren't "reused" in cells a few miles away as the hundreds of cellular channels are today... you had to be out of range of a 25 watt transmitter before another town could reuse one of the channels. I was YS3-7429, registered in San Jose, CA., back when you still talked to an operator to place a call.