Here's a great, simple Make project that teaches you how to make an intercom from a pair of old, corded phones, a 9V battery and a resistor. I loved walkie-talkies and intercoms when I was a kid -- the idea of setting up your own house-wide wireline intercom is super-cool, and the project is dead-simple.
At its most basic level, a telephone network is just two microphones, two speakers and a power source. In this project we are reducing the phone to these basic elements. The handset of the phone contains the speaker, the microphone and any necessary processing circuitry. All we need to add is the power source.
A regular corded telephone doesn't require much electricity to operate. It just needs about 9 volts and less than 30mA. It normally gets this from the phone line itself. This is why many phones can still work even during a blackout. However in this project, we are using a single 9 volt battery to power our phones.
The battery is wired in series with a 300 ohm resistor and connected to either the red wire or the green wire in a phone cord. The phone cord is then plugged into both phones. The battery is able to supply enough electricity to power the speaker and microphone circuits of both phones. This allows you to use them to talk back and forth.
Simple Intercom From a Pair of Old Corded Phones [Jason Poel Smith/Make]
Thinkgeek is accepting pre-orders for six upcoming 14 oz Star Wars tiki mugs, standing 6.5″-7.5″ tall, with contrast-glazed interiors.
Chloe from Portland’s Reading Frenzy writes, “Six of our favorite Social Justice Kittens are back in postcard form! Next up: MRA Puppies! Postcards by Sean Tejaratchi/LiarTownUSA (previously) published by Show & Tell Press!”
You’ll know Ben Hatke as author of Boing Boing-beloved illustrated kids’ books like Little Robot and Zita the Space Girl, but as this Children’s Book Week video shows, Hatke is a literal fire-breathing, acrobatic, sword-fighting superhero!
White hat hackers get paid to find holes in their own employers’ online systems, and plug those holes before they become serious security risks. It’s a job that pays handsomely…mostly because few job candidates, even experienced IT professionals, have the skills to scamper over firewalls and infiltrate the deepest recesses of a battle-tested network. But […]
Why buy one of those expensive and confusing universal remotes, clogged with enough buttons to launch a space shuttle, when you could accomplish the same electronic control right on your favorite mobile device? The Blumoo Universal Remote, now just $52.99 in the Boing Boing Store, harnesses the audio power of all your household equipment right […]
You may not love Microsoft Word, but you’ve definitely used it. Other than being one of the most ubiquitous programs on the planet, it’s been the go-to word processing system for more than a quarter-century because it’s as basic as it gets. But occasionally, you’ve got assignments that beg for a lot more options than simple […]