The following has an article from the Bell Laboratories Record about the original telephone service provided on the Penn Central Metroliner trains in 1969. This was the first application of the "cell" concept of re-using radio frequencies and shifting frequencies as the vehicle is in motion. While we take cell phones for granted these days, in
1969 the Metroliner service was a major technical advancement. There were passenger radio-trainphones before Metroliner, but they were limited.The article notes:
- The system was two-way. Land based people could call any train by giving the train number, location was not necessary. The equipment automatically located the desired train along the route. An attendant answered the call and paged the desired passenger.
- Calls could be paid by collect, credit card, or coin.
- Passengers would dial direct on a Touch Tone. Direct dialing and Touch Tone on coin phones was a new concept in 1969.
- Service was provided in the five Baltimore tunnels and under Phila
30th Street by special antenna work designed for the underground environment. I don't think service was provided in the Hudson River tunnels.- As mentioned, the system was cellular. The article describes some technical details on radio transmission within the cells and separation of the cells.
- Because calling traffic was expected to be heavy as the train approached its end terminals, additional channel capacity was provided in those areas.
- The train transmitters produce 12 watts of RF power.
- Every phone on a car is independent of other phones on a train.
- The system accounts for variation of train battery supply from 56 to
88 volts.- The car antenna was protected from sharp brushes used in the carwash and noise from the 11KV AC pantograph arcs and power cable.
- Base station transmission power design took into account terrain, antenna heights, and distances between base stations so as to maximize the signal up to cell boundaries but not far beyond.