This repair/tutorial video by the telephone Connections Museum of Seattle features an amazing piece of electro-mechanical technology from the 1950s — the 5XB trouble recorder. Museum volunteer Sarah the “Switch Witch” has a deep passion for old phone equipment, and gives an excellent description of the trouble recorder, the problems it solved, and how it works, and how they went about fixing it.
As central office switching became more complex and more dense, the manual methods of hunting down faults became unmanageable. Semi-automatic approaches using trouble lamps, but even that had its limits. This “stack trace”, which could have hundreds of indicators, had to be frozen while the technician recorded the status on a form. If another fault came along during this time, it was lost. The solution, using the available technology of the day, was a mind-boggling punched card apparatus that punches over a thousand bits of information when an switching error is detected or when various watchdog timers expire.
Continue reading “Stack Trace From The 1950s Punches Again”
I can’t help but wonder how long it will be before the movie title “Dial M for Murder” becomes mysterious to most of the population. After all, who has seen a dial phone lately? Sure, there are a few retro phones, but they aren’t in widespread use. It may not be murder, but it turns out that the dial telephone has its roots in death — or at least the business of death. But to understand why that’s true, you need to go back to the early days of the telephone.
Did you ever make a tin can phone with a string when you were a kid? That dates back to at least 1667. Prior to the invention of what we think of as the telephone, these acoustic phones were actually used for specialized purposes.
We all know that [Alexander Graham Bell] made a working telephone over a wire, drawing inspiration from the telegraph system. However, there’s a lot of dispute and many others about the same time were working on similar devices. It is probably more accurate to say that [Bell] was the first to successfully patent the telephone (in 1876, to be exact).
Continue reading “Rotary Phones And The Birth Of A Network”