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.
This handheld magnifying glass has two bright LEDs and is powered by 3 AAA cells (not included). The manufacturer says the magnification is 40X. I think it is less than that, but it is still plenty powerful for my needs – mainly, reading the markings on tiny electrical components and checking the layer fusion on […]
The curved bottom of the cup peeks through your drink as the level drops down, moving the “moon” from full to a fingernail-paring sliver. Of course, it works better if you drink something cloudy and white — it’s designed some cloudy Korean rice-wines, but would also work with Pernod and water, I’m thinking.
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Power up your gadgets in the most unexpected places with the extremely compact SolarJuice battery pack. SolarJuice charges up at home like your average battery pack, but also lets you add extra juice on-the-go using its built-in solar panel—so you’ll never be left unplugged from the digital world.4.5 Stars on Amazon!Simultaneously charges 2 devices at […]
Hold your camera to higher standards with the brand-new iBlazr 2, the most advanced LED flash to date. Simply attach to your smartphone, tablet, or DSLR camera. Conveniently sized and wireless, this premium flash will let you easily take amazing photos in low light situations. It’s a literal snap to use: simply attach to your […]