Firefox, Chrome Patch Vulnerabilities, Add Security Features
Dueling browsers, Mozilla Firefox and Google Chrome, have patched bugs and beefed up security. Continue reading Firefox, Chrome Patch Vulnerabilities, Add Security Features
Category Archives: dtmf
In-Band Signaling: Dual-Tone Multifrequency Dialing
One late night many decades ago, I chanced upon a technical description of the Touch-Tone system. The book I was reading had an explanation of how each key on a telephone sends a combination of two tones down the wire, and what’s more, it listed the seven audio frequencies needed for the standard 12-key dial pad. I gazed over at my Commodore 64, and inspiration hit — if I can use two of the C64’s three audio channels to generate the dual tones, I bet I can dial the phone! I sprang out of bed and started pecking out a …read more
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Fake Ram: Identifying a Counterfeit Chip
[Robert Baruch] had something strange on his hands. He had carefully decapped 74LS189 16×4 static RAM, only to find that it wasn’t a RAM at all. The silicon die inside the plastic package even had analog elements, which is not what one would expect to find in an SRAM. But what was it? A quick tweet brought in the cavalry, in the form of chip analysis expert [Ken Shirriff].
[Ken] immediately realized the part [Robert] had uncovered wasn’t a 74 series chip at all. The power and ground pins were in the wrong places. Even the transistors were small CMOS …read more
Automatic Phone Dialer Illuminates Inner Workings
The invention of the transistor ushered in a lot of technologies that we now take for granted, and one of the less-thought-about areas that it improved living conditions worldwide was by making the touch-tone phone possible. No longer would the world have to fuss with dials to make phone calls, they could simply push some buttons. This technology is still in use today, and it is possible to build external phone dialers that use these tones to make phone calls, as [SunFounder] demonstrates with his latest project.
The tones that a phone makes when a button is pressed correlate with …read more
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