Monthly Archives: October 2012

Asterisk and Cisco 7940

There are a number of guides out on the Internet for getting Cisco phones working with Asterisk. I didn’t particularly find any of them 100% thorough. This then is my guide, documenting the moment I ordered the phone to the moment I made a call on it. I bought a Cisco 7940 phone from eBay.… Read More »

Software Defined Radio (RTLSDR) — Part I

A quick (simple) word first on how radio receivers work. A “message” is created at so-called “baseband”. You can think of it, if you like, as the signal that comes from the microphone in the radio studio. That message is used to modulate a carrier wave. A carrier wave is a pure sinusoid at a… Read More »

WordPress Fight

A quick note in case it helps someone else using WordPress. I had a bit of a fight trying to get WordPress to output the HTML that it was given for a post unaltered, this article records what I did. I write these articles in markdown syntax, then convert them to HTML using pandoc. One… Read More »

Units of Measurement

I am generally all for not legislating anything, but the world really does need to use a commonly agreed system for physical measurements. That system is, like it or not, metric. Or rather SI units. I am sure I am not alone in thinking that some mistakes were made in the SI unit system —… Read More »

Pushmepullyou: Discount for Cash

I’ve touched on the idea before, but I thought it was time I made it explicit. I want to compare customer-not-present purchases using bitcoins and using credit cards. In particular: security. Consider a modern web site, accepting a credit card. You fill up your basket and press “buy”. You have to supply: Name Address Email… Read More »

Child Gender Ratios

There’s a country where everybody wants to have a son. Therefore each couple keeps having children until they have a boy; then they stop. What fraction of the population is female? (You may assume the question is asked as an expectation of course, since any particular country can be anything in principle — 100% girls… Read More »