Songfacts®:

• Before smartphones, if you called a phone that wasn't hooked up to an answering machine it would just ring and ring until you hung up. That's what's happening in this song, where Electric Light Orchestra leader Jeff Lynne is desperately calling a girl who either isn't home or won't pick up.
  
  "I sound really desperate and lonely on this one, and maybe I was," he told Rolling Stone. "It's about trying to find a girl every night and you just can't get through to her. It was a scenario I thought of, but maybe it was prompted by the fact that I wasn't happy at the time."
• The song starts with the sounds of a ringing phone, and when the vocals come in, their distorted to sound like they're coming over a telephone line. As Jeff Lynne sings the first verse, he becomes more clear, finally achieving full fidelity as the strings kick in. Electric Light Orchestra's songs are very expansive musically, so starting it with a telephone effect draws a strong contrast and also sets up the story in the song.
• This song was inspired by the music of Roy Orbison, who released some of the saddest songs of the '60s - tunes like "Crying" and "Only The Lonely." Jeff Lynne later teamed with Orbison in the supergroup The Traveling Wilburys.
• There's a healthy helping of nonsense vocals in the pre-chorus:
  
  Doo wop, doo-bee-doo doo wop, doo wah, doo lang
  Blue days, black nights, doo wah, doo lang
  
  These kind of vocalizations were common in doo-wop songs from the '50s and '60s like "Blue Moon" and "Book Of Love." What's interesting here is how Jeff Lynne slips in something meaningful with "blue days, black nights." It a kind of scattered depression that gives us an insight into this guy's mental state, and it's not pretty.
• "Telephone Line" is part of ELO's sixth album, A New World Record, released in 1976 when they were starting a run of hits that includes "Livin' Thing" and "Mr. Blue Sky." They're a British band but they were really popular in America as well - note that the telephone sounds in the song are what you'd hear on an American call, not on one to Europe.