Apr 132013
 
Keyboard

A Glance at Computer Keyboard

Keyboards are one of the most important input devices which are used in feeding input to computers. They are designed for the input of texts and characters, and also to control the operation of the computers. The most common and widely used arrangements of keys in many countries are based on the QWERTY layout. The number of keys on a keyboard generally varies from the standard 101 keys and 104-key Windows keyboards, to as many as 130 keys, with many programmable keys.

A computer keyboard is effectively an array of different switches and buttons, each of which sends the computer a unique type of signal when pressed. The switches are generally kept in a keyboard by the means of either mechanical manner or a rubber membrane.


The keys kept in mechanical manner are simply spring-loaded. They are of ‘push-to-make’ types. This means that when they are pressed down, they complete the circuit and then break it again when they are released. Likewise, the keys kept on a rubber membrane are composed of three different sheets. The first sheet has conductive tracks printed on it, the second is a separator with holes in it and the third is a

conductive layer with bumps on it. A rubber mat over this gives a springy feeling. When a key is pressed, it pushes the two conductive layers together to complete the circuit. On the top is a plastic housing which includes sliders to keep the keys aligned.

A dome-switch keyboard is commonly used variation of the membrane-type keyboard. With these, a key depression pushes down on a rubber dome sitting beneath the key. A conductive contact on the underside of the dome touches and hence connects a pair of conductive lines on the circuit below. This bridges the gap between them and allows current to flow by changing the signal strength. A scanning signal is emitted by the chip along the pairs of lines to all the keys. When the signal in one pair becomes different, the chip generates a ‘make code’ corresponding to the key connected to that pair of lines. The code generated is sent to the computer either through a keyboard cable (using on-off electrical pulses to represent bits) or over a wireless connection. A chip inside the computer receives the signal bits and decodes them into the appropriate key press. The computer then decides what to do on the basis of key pressed.

The keys are connected up with each other like a matrix, and their row and column signals feed into the keyboard’s own micro-controller chip. This is mounted on a circuit board inside the keyboard, and interprets the signals with its built-in firmware program. A particular key press might signal as row 3, column B, so the controller might decode this as an A and send the appropriate code for A back to the computer. These ‘scan codes’ are defined as standards in the computer’s BIOS (Basic Input Output System), though the row and column definitions are specific only to that particular keyboard.

Apr 112013
 

Two Nepali businessmen once duped US diplomats by offering Uranium deals claimed to have been smuggled from a nuclear facility in India, according to diplomatic cables recently released by Wikileaks.

In September1973, one JC Thakur approached the US Embassy in Kathmandu and claimed that he could deliver 2 to 3 kg of Uranium at $40,000 per kg. The samples of the

purported radioactive element were collected by US Embassy officials and were sent to the US-based Atomic Energy Commission for verification, according to the cables.

A cable forwarded on September 26 that year said Thakur, in a meeting with the embassy officials, expressed willingness to offer samples for analysis and briefly showed them a small amount of a brown substance packed in a small plastic vial. When inquired about the source, he indicated that the uranium would be smuggled out to him from nuclear power facilities in Bombay (present day Mumbai).

A day after the cable detailing Thakur’s attempt to sale the element was forwarded to the State Department in Washington, the US Embassy in New Delhi suggested that the information be shared with the Indian government. The cable dispatched on September 27 asserts that such a move would contribute to the atmosphere of trust and confidence with India for the peaceful use of nuclear energy.
A cable later sent by Washington gives a green signal to collect the samples from the traders in Kathmandu. It also instructs the embassy officials to send it to the US through a ‘small diplomatic pouch’ and advises the embassy in New Delhi to use its “discretion” in apprising the Indian government ‘informally of the offer.’ Thakur himself contacts US embassy officials in Kathmandu on October 7 and visits them the next day to hand over the samples. The communiqué notes that in the second meeting, Thakur stressed the need for ‘secrecy,’ saying that the issue is a ‘life or death situation for him and his partner,’ according to the leaked cables. He also says he can provide 5 kg of enriched Uranium per month for $35,000 per kg, a rate cheaper by $5,000 than the one mentioned in the first meeting.

The reply from State Department on October 16 says that the sample was not radioactive, hence it was not likely to be uranium. Before the announcement of the result, the US Embassy in New Delhi informed the Coordination Director of India’s External Affairs Ministry of Thakur and his attempt to sale smuggled uranium.

US diplomats later found out that Thakur was the brother of Prakash Chand Thakur, the former Nepali ambassador to Japan who was recalled for drug abuse, and concluded that the incident was part of an ‘elaborate hoax’ perpetrated on them.
A cable sent from Kathmandu in August 1975 states that Thakur was trying to test the samples for free and ascertain whether Uranium exists in the Nagarjun hills in Kathmandu.

In October 1973, the US embassy in Kathmandu is contacted by another individual named Krishna Tamang who hands over a sample, claiming that he can supply 10 kg of uranium per month for $5,000 a kg. It notes that Tamang was highly nervous in the October 18 meeting and said that he received the substance from his partner in India. Tests of the sample handed over by Tamang confirmed in November that it was not uranium. The State Department in Washington then draws the attention of its embassy in India and Nepal to the matter and asks them not to consider the ‘hoax offers’ but accept samples, if offered. A cable sent from New Delhi in May 1974 quotes the then Indian Minister of State KC Pant as informing the Rajya Sabha that five persons were arrested and 750 grams of yellow powder, said to be uranium but later verified as sulfur, was obtained during a raid in Jamshedpur in South Bihar.

The police action in the state of Bihar reminded the US diplomats in New Delhi of the purported uranium deal of September 1973, who said the ‘silly season’ for uranium deals were yet to be over.

Again in September 1975, Krishna Tamang visited a US Embassy official in Kathmandu and offered two vials of a reddish powdery substance for testing.

Considering Tamang’s old record, both the embassy and the State Department concurred that they would not forward it for testing.

By: Phanindra Dahal (The Kathmandu Post), eKantipur