delay pools

Sorry for not looking harder, but can someone point me to a resource
that explains delay pools in a little depth? I'm having trouble working
out the different classes and the various options. The FAQ was pretty
sparse as was the config file, and I'm too lazy to read the source.

All I want is to limit modem users (on a /28) to 8kb/sec.

I tried it once, using delay_class1, and was quite happy with the
results, seeing bandwidth usage halve. Unfortunately I think I was
restricting the whole modem pool to 8kb/sec :)

Thanks,
Chuck

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error writing to /dev/chuckd: device busy