Before the rise of broadcasting, it appeared that the most promising use for radiotelephony would be for personal mobile communication. But although carphones would see a limited development over the next half-century, it wouldn't be until the 1980s that they started to become common.

Special thanks to Donna L. Halper for providing a copy of the original article.
 
Boston Sunday Post, Woman's Section, November 7, 1920:

Talking  by  Wireless  as  You  Travel  by  Train  or  Motor
    It is now possible for a business man to talk with his office from a moving vehicle.
    While touring in his automobile or riding on a train for instance he can communicate by word of mouth with his secretary. The apparatus necessary to do this marvellous thing can be carried in a small dress suit case.
    Prof. Harold J. Power, wireless wizard and directing genius of the American Radio and Research Corporation, keeps in touch with his office while enjoying recreation in his automobile.
    Today he tells Sunday Post readers how he does it and discusses the problems to be overcome in developing the radiophone for practical general use.
 
By John T Brady

    Professor Harold J. Power was speeding toward Winchester in his automobile.
    I was seated in his office at Medford.
    Miles separated us--he was traveling along the highway at 25 miles an hour--yet we had no difficulty in talking by radiophone.
    It was a unique method of making an appointment for an interview--the most novel experience in my decade of newspaper work.
radiotelephone equipment
    And here is how it happened.
    Rising to a height of 304 feet on the side of College Hill at Tufts is a sky-piercing skeleton of steel.
    The casual inquirer is told that this is a wireless aerial, but it is more.
    It is the ladder up which Harold J. Power has climbed to fame as a radio-engineer.
    The sun was slipping behind College Hill and the shadow of the big steel mast was rapidly lengthening--in other words, it was late in the afternoon when I stepped into the main office of the American Radio and Research Corporation at Medford, seeking an interview with the general manager of the plant, Professor Harold J. Power, called "H.  J." by everybody from the office boy up.
    "Professor Power is on his way to the Country Club at Winchester in his automobile," said his polite secretary, Mr. Barrow.
    "Would it be possible to have a talk with him in the morning?" I inquired, disappointed.
    "You can talk with him now by radiophone if you'd care to try the experiment," replied Mr. Barrow.
    "You don't mean it's possible to phone to him while he is speeding along the highway," I said incredulously.
    "Certainly," replied Mr. Barrow smiling. "Our motto here is 'nothing is impossible, though some things are impractical.' "

Start  Talk  at  "Zero  Hour"

    "Here put on this head-piece," he directed, handing me a telephone set such as switchboard operators use with receivers for both ears and a mouthpiece that rested on my chest.
    As I donned the head-piece he laid his watch on the desk in front of me.
    "Nice of him to display such confidence in my honesty," I thought, estimating the timepiece to be a valuable one.
    The time was 3:59.
    "Precisely at 4 o'clock, speak into the transmitter naturally and distinctly, just as you would into an ordinary telephone," he explained.
    "What shall I say?" I inquired.
    "Well, that sounds funny coming from a newspaper man." he said with a laugh. "I never expected to catch a reporter at a loss for words. Say anything you like. Perhaps you can make an appointment with Mr. Power for an interview tomorrow or next day."
    While a minute elapsed very slowly Mr. Barrow was busy. He placed a mahogany box about 10 inches square on one end of the desk and connected to it wires running to a series of small storage batteries and a generator in one corner of the room. Another wire running out the window of the office to the wireless aerial that I could see in the distance was connected with the box and the stage was all set for the novel experiment.
    It was 4 o'clock.
    "Go ahead, speak and don't shout," said Mr. Barrow.
    "Hello! Hello! Is this Professor Power?" I asked.
    Mr. Barrow pulled a little lever on the side of the box at my elbow.

How  It  Is  Done

    "Now, listen." he said.
    The answer to my query, sent out on the wings of the wind through the agency of electrons--smaller than atoms--flying about in a real Aladdin's lamp, came clear as a bell in the still of the evening.
    "Yes! Yes! This is Power. Who is this calling?"
    "Mr. Brady of the Boston Sunday Post staff. I should like to interview you tomorrow," I said, when Mr. Barrow had again manipulated the switch on his mystery box.
    "All right. Make arrangements with Barrow as to the time." was the reply.
    "Ask him where he is now?" suggested Mr. Barrow.
    "Where are you now?" I asked.
    "Just skirting Mystic Lake," was the answer. "Tell Barrow to tune up again at 5 o'clock. I'll be listening. Good-by."
    I had arranged for an interview by wireless telephone. Every word that Professor [Power] had uttered was deposited in my ears softly and distinctly. Even the modulations of his voice were distinguishable, and I feel sure he heard and understood everything I had said. With the exception that I could not talk back to Professor Power until Mr. Barrow had thrown a switch, and that we could not talk and listen at the same time, the conversation was no different from that over an ordinary telephone.
    By using double aerials we might have overcome this inconvenience, according to my young friend, Stanley Day of Saugus, a promising 16-year-old in the wireless field, with whom I later discussed my experience.

Giving  Morgan  a  Concert

    There has been much in the headlines lately about sending music by wireless. "Jimmy" Power did that back in 1916. On March 18 of that year he held a concert in a little building at the foot of the wireless tower at Tufts College for the entertainment of a traveller on the high seas.
    The traveller was J. Pierpont Morgan of New York, who was on his way home from a mission to England in connection with the financing of the World war. He was on board the American line steamer Philadelphia.
    Professor Power, then professor of radio engineering at Tufts, was formerly a wireless operator on Mr. Morgan's private yacht, the Corsair, and he decided to give his former employer a surprise.
    When the big liner was about 75 miles off Cape Cod a call was sent to her by wireless asking that Mr. Morgan be informed of what was to be undertaken. Going to the ship's wireless room, the millionaire was handed a receiving set, and for the next three hours, from 8 to 11 o'clock, he listened to a concert such as no other mortal had ever heard under similar circumstances.
    "What are the problems to be overcome in making the wireless telephone practical for general use?" I inquired when I met Professor Power the next day.
    "Perfection of a good signalling device and the problem of selectivity." he said.
    "At present the person making a call by wireless telephone has no way of signaling the person he desires to talk with. The party called must be listening for the message. That explains why a definite time for conversing by radiophone must be fixed beforehand.
    "This obstacle in the development of the radiophone will be overcome by the perfection of a ringing device or a light signal such as is now used the ordinary telephone systems for attracting the attention of the operator at the switchboard in the central station.

Selectivity  Problem  to  Be  Solved

    "The problem of selectivity will be harder to solve." said Professor Power as he drew several criss-cross lines on a sheet of paper with his pencil.
    "A radiophone system would be very popular in a country town, as everybody can hear what everybody else is saying simply by properly tuning their receiving apparatus," said Professor Power, laughing.
    "These lines illustrate radiophone messages going through the air in all directions." he said, holding up the drawing he had made. "The problem is to make them selective, that is, to prevent Tom, Dick and Harry who has a receiving set from listening in on any conversation that sounds interesting."
    "Like love talk," I suggested.
    "Yes." he said, smiling. "Lovers ought to learn a code if they intend using the radiophone to exchange 'sweet nothings.' "
    "Don't they use a code of their own now?" I asked.
    "Yes," he replied, "but it is one that is universally understood."