Wednesday, January 28, 2009
In its original incarnation, the BNC was designed for RF applications and had a characteristic impedance of 50 ohms, together with a predictable reflection factor. Increasing use in applications such as video equipment, with source and load impedance of 75 ohm and with 75 ohm cables, led inevitably to the creation of the 75 ohm BNC.
At frequencies of up to 10MHz, the characteristic impedance of the connector is completely swamped by the source and load impedance of the circuit of which it is part, thus in analogue video applications it is simply irrelevant whether a 50ohm or a 75ohm connector is used. However the increasing likelihood that the connector is being fitted in a digital video application means that it is absolutely essential that 75ohm connectors and cable are used. This requirement is becoming ever more important as the introduction of HDTV requires significantly higher bit rates so the demands on the cable and connector infrastructure increases.
Tuesday, January 27, 2009
- Graphics tablet expensive (though prices have come down), need to trace over drawing, need flat surface
- Digital camera - good, but need to take out camera, then connect to computer and download image
- Bingo! Use built in iSight to take digital snaps of sketches and store in research manager!
Monday, January 26, 2009
Subject: Free stuff
Date: Tue, 1 Jul 2008 10:01:15 -0400
There are free lab supplies and equipment outside room XXX. Please help yourselves. Also please do not take the cart.
Saturday, January 24, 2009
Saturday, January 17, 2009
|Prefix/Suffix||Meaning and remarks|
|TM Ø||Tinctura Mater (Mother Tincture) Ø = Theta which is the 8th letter of the Greek alphabet and denotes a 1:10 dilution. The orthodox abbreviation for a tincture is Tr.|
|D or X||Dilutions made on the decimal scale i.e., 1:10. The 'D' is taken from the metric prefix meaning one tenth (1/10). The 'X' is taken from the Roman numeral meaning 10 and was introduced by Constantine Hering.|
|C or c||The 'C' was taken from the Roman numeral meaning 100 and the lower case 'c' from the metric scale meaning one hundredth (1/100). See Table 5-16A.|
|CM|| Roman numerals i.e., C = 100 M = 1000 |
Homeopathic meaning 1:100,000 One hundredth millesimal.
|LM sometimes |
as 0/1 , 0/2, etc.
| Roman numerals again i.e., L =50 LM = 50,000 |
Homeopathic meaning 1:50,000 The 50th millesimal.
|MM||Roman numerals, Homeopathic meaning 1:1000,000 Thousandth millesimal|
|M||Millesimal meaning 1:000|
|H||Hahnemann's method of potentisation|
|K||A method of potentisation which was introduced by a Russian General by the name of von Korsakoff in 1829, probably as a labor saving method. However, it produces inacuracies against the Hahnemannian method, so a question mark hangs over it.|
- fdisk /mbr and fixmbr will fix the MBR but not necessarily get rid of any viruses in it [msoft].
- Use the Ultimate Boot CD which has a bunch of low level HD tools from various manufacturers to zero fill the drive, erasing the MBR and any other possible hiding places for the virus. I used the iso found at mrbass.org.
I decided that my parents computer was infected by a boot sector virus because:
- Installation of Linux or Windows XP went fine from CD.
- After the first reboot win xp or linux would stop working and freeze during bootup
- I could get winxp working again by booting into recovery mode and using fixmbr
- A scan by the seagate tools did not uncover any errors in the disk
Enter the command: "FIXMBR" (without the quotes) at the input prompt and confirm the next question with a "Y" (without the quotes). Use exit to restore the computer.
Friday, January 16, 2009
- Open a DOS Command Prompt
- Type "nslookup".
- Your computer's DNS Server name and IP address will be displayed.
- Type "set type=mx" - This will cause NSLOOKUP to only return what are known as MX (Mail eXchange) records from the DNS servers.
- For an example, type "hotmail.com" or use your own domain name.
- Results returned should look similar to this:
hotmail.com MX preference = 5, mail exchanger = mx2.hotmail.com
hotmail.com MX preference = 5, mail exchanger = mx3.hotmail.com
hotmail.com MX preference = 5, mail exchanger = mx4.hotmail.com
hotmail.com MX preference = 5, mail exchanger = mx1.hotmail.com
Wednesday, January 14, 2009
 In the Netherlands, Saudi Arabia and India, the caller ID standard is DTMF. In the US it is the Bellcore FSK standard and in Germany it is the ETSI FSK standard.
The US also transmits both the user name and the phone number whereas the Indian system transmits just the phone number [artech].
 A DTMF to FSK converter is needed. Artech manufactures these calling them Caller ID Converter, DTMF to FSK. The model number is EX230.
Sunday, January 4, 2009
The following facts may all be relevant or useful to other people:
- I had an unexpired (but invalid) F-1 visa in my passport.
- I no longer have a valid I-20
- I changed status from F-1 to H-1B while within the US
- I did not have a H-1B stamp in my passport
- My stopover time was 2 hours (as a side note, I would not recommend a shorter transit time because you have to go through security again)
- My connecting flight was from the same terminal and the same airline
- The only person who checked my passport for visas was the BA desk clerk at Logan
- At Heathrow the passport is only used to verify identity
- No one asked for an I-20 (I recall vaguely someone asked for an I-20 at Heathrow last time I came to the US via London, but I don't recall if they actually looked at it or merely reminded me that I would need it in the US)
- I did NOT need a transit visa