Recently, I got to spend a week learning how to be a phoneman (let’s just pretend that this is gender neutral). It’s a long story, but every member of research at AT&T Labs is expected to also pick up an essential trade within the company and get trained to be able to perform one of these core services. These training sessions are done by experienced AT&T employees who have been at the company for decades and can impart on us some of what they term as “phoneman sense.”
A section of the cable that runs under the ocean.
My favorite part of the training was getting a much better idea of how data is actually transmitted around the world. I am now convinced that the communication network is the most ambitious endeavor attempted by humans: more reliable than the power grid, stretching across the world and even into the orbit, and maintained by hundreds of thousands (millions?) of individuals world-wide. The thing that really blew my mind was thinking about how much data can be transmitted over a single cable. In the beginning, there was just a pair of copper cables: your voice was sampled on one side, each sample converted to a number, and the number was sent as binary code over the wire by varying the voltage. Easy-peasy! This is known as a DS0 connection and it transmits 64 Kb/s. But it didn’t stop there, once the wires come out of your house, somehow data from all the phones in your neighborhood needs to be combined to be sent to the central office. This is done by taking a byte off each wire and multiplexing them.
In training, I got to get decked out in all the safety gear that I would wear for working with batteries and other hazards.
Combining 24 DS0 connection in this way, makes your standard DS1 connection which transmits 1.5 Mb/s. At this point, the connection is frequently no longer transmitting over a wire but rather through an optical cable, by flashing a laser light for 1s and not flashing it for 0s. At this point, I was already pretty impressed — doing anything 1,500,000 times per second just seems like a big deal. But, it doesn’t stop there. Three DS3s (and some info bits wrapping the data) are combined into an OC-3 connection,12 DS3s are combined into an OC-12, and so on until you have the OC-192 which transmits 192 DS3s by flashing a laser 9,953,000,000 times a second! Over a single cable that’s thinner than a human hair! Maybe I’m too easy to impress, but this totally blew my mind! I can’t even wrap my head around that number, let alone imagine doing something purposeful that many times a second. And this is happening every single moment in your back yard!
It’s pretty cool to potentially be part of this, even as a tiny cog in the machine. I learned some good stuff like how to maintain the systems that do all of that multiplexing and maintain service in a power outage by hooking up generators and maintaining the batteries at remote terminals. It really makes me appreciate all of the stuff that goes on behind the scenes to make sure that I always have access to my lolcats.
