Web kiloseven.blogspot.com
www.arrl.org www.eham.net

2011-09-30

A+ More on IP addresses

IP (Internet Protocol) addresses are 'hierarchical'; like phone numbers, where the area code and the first two digits of the phone number can tell you where the phone number is (like 305 is Miami and 503 is NW Oregon)
      (except for numbers which have been Ported, but don't get me started on THAT infernally bad idea).

IP addresses also group and can be identified by the nation and the ISP which issue them, at sites like http://tools.whois.net/whoisbyip.

Every packet of Internet data contains the IP address the packet is supposed to go to, as well as the Software Port it's supposed to arrive at, and the Protocol (ICMP, UDP or TCP) which will use the data.

Popular ports include 20 and 21 for FTP, 23 for Telnet, 25 for SMTP, 53 for DNS (the 'white pages' of the Internet), 67 for SMTP, 80 for HTTP, 110 for POP, 443 for HTTPS, 1863 for the Kinect and 3074 for the Xbox. RFC 1597 outlines the most popular port assignments, and you can see those at iana.org/assignments/port-numbers.

DNS looks up www.whatever and finds an IP address for it, and if it can't find an address, it goes and asks another DNS server.

Labels:

2011-09-28

A+ laptop power tips

A+ laptop power tips: Power supplies can be built in to laptops but the current fashion is to put them in an external 'brick'. This puts the largest source of waste heat outside the laptop itself.

The laptop's serial number label normally has the specification for the power supply, although it can be printed elsewhere on the laptop underside. Adapters can be substituted as long as you follow these rules:

1) AC does not equal DC: If the output voltage specification calls for AC, the adapter must provide AC; if DC is called for, make sure the replacement provides DC.

2) The output voltage must be within 5% of the specification and should be the same voltage.

3) The wattage or amperage (watts/volts) of the replacement must be at least as much as the original specification. If you replace a power supply with a higher-wattage or higher-amperage supply, that's OK.

Labels:

2011-09-21

A+: Laptop Batteries and best care for long life

A+: Laptop Batteries and best care for long life

Batteries left in a laptop that's running all the time will 'cook' by exposure to the heat of a running laptop 24/7 and lose lifetime capacity. Therefore, once charged, if your laptop will boot up without a battery and you're using it on AC, that's OK; otherwise, set your laptop to sleep or hibernate when idle so your battery lasts longer.

Four major types of batteries are used nowadays to power laptops; lead-acid batteries are passe and throwaway alkaline or lithium batteries could be used in a handmade external battery pack (say for long flights) but the sturmtruppen of the TSA might look askance at such a practical device.

WARNING: BATTERIES ARE TOXIC, AND CAN CATCH FIRE. DISPOSE OF PROPERLY.

We commonly find in laptop use (oldest to newest):

NiCD AKA Nickel-Cadmium - a complete discharge/recharge every 30 uses is a good idea. They drain down by themselves 10%/month and can last for a thousand cycles or more.

NiMH AKA Nickel Metal Hydride - a complete discharge/recharge every 30 uses is a good idea. They only store 40% as much charge per pound as NiCD batteries, self-discharge around 15%/mo and only last 500+ cycles.

Li-Ion AKA Lithium Ion - these should be completely discharged and recharged when the charge drops rapidly from 30% to 0%. It's OK to partially recharge/discharge them, they're much less fussy about needing a full discharge-recharge cycle than the Nickel batteries.

Li-Poly AKA Lithium Polymer - these store less charge per weight than Li-Ion but are more flexible and can be formed into complex shapes (I'm wearing one, like a wrist watch, right now).

Labels: