This 7403 (quad two input OC nand) has been sitting around since the 35th week of 1974 and I've finally found a use for it.
This IC has been hanging around for so long because I almost never needed open collector outputs, but for today's project those outputs are at last exactly what I do need. It pleases me no end that I've just found a use for one of the parts that I bought when I first started doing electronics as a hobby.
I'm using this to ensure that two relays which should never be switched on at once actually never can be switched on at once, no matter what happens with a software crash, bug, or whatever. It'll be used in the ventilation controller that I'm currently building.
TTL chips made in 1974 are especially cursed because it's so easy to mistake them for something else.
None of your fancy modern LS here, at least so long as you don't look at the rest of the circuit which uses relatively modern stuff to do the actual "thinking". #electronics#ttl#TexasInstruments#ttldatabook#7403
For a lecture dealing with DNS, I am trying to find a ballpark estimate of how often a DNS record gets updated. (In order to show how hosts.txt would never scale).
Up to date ballpark estimates of the current number of records on the internet are also appreciated.
Retoots while prevent a new Morris worm to ask all DNS servers to report the count in their zones :D
@Sobex most hosters' #TTL of a #DNS record is 3600s = 1h, but depending on the exact setups can be far lower for round-robin DNS.
I've seen some as low as 60s = 1min in some #API-based systems that use transparent DNS to load-balance as well as #anycast the request to the nearest node that is online...
Not to mention that even if we'd only have #IPv4 and only use each #IP and #FQDN once and every entry was just 128 bytes, we'd have ~ 512GB for a #hosts file...
Anyone got any tips on monitoring every pin (CTS, DTR, etc) on an #RS232 connection when you only have a cheap Cypress #logicanalyser?
I'm guessing I'm going to need to get a handful of RS232 to #TTL converters so that I don't blow up the analyser with ±12V. But if anyone has a better solution, I'm all ears.