Linksys WRT54G, about 250 feet.
Big determining factor is the construction of the house and sources of noise or interference (most cordless phone are 2.4GHZ which can screw things up, microwave can disrupt the signal, high voltage sources nearby, other wireless networks on the same frequency etc...)
The distances the manufacturer states are made in an idea situation. Don't believe everything you read.
I do think 424 feet is probably an unrealistic expectation unless you raise toss in a booster and raise the router above all other structures in the area.
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