From Chennai US Consulate website:

Any person holding a B1 or B1/B2 visa may be eligible to perform H-1B work in the United States as long as they fulfill the following criteria:

• Hold the equivalent of a U.S. bachelor’s degree
• Plan to perform H-1B-caliber work or training
• Will be paid only by their foreign employer, except reimbursement of incidental travel costs such as housing and per diem. The employee must not receive any salary from a U.S. source.
• The task can be accomplished in a short period of time.

These travelers would be admitted as B1 visitors, and may only stay in the U.S. for the time allotted by the Department of Homeland Security upon entry.

Like any other B1/B2 applicant, travelers must still show strong professional, familial and financial or other ties, which indicate a strong inducement to return to the country of origin or another country other than the United States.

Consulate General Chennai is prepared to issue B1/B2 visas to qualified applicants for this purpose. These visas may also be used for tourism. Current holders of B1/B2 visas may already use this provision without seeking another visa.

When seeking a visa for this purpose, please clearly explain this in the applicant’s BEP cover letter.

If the applicant and employer so chooses, they may also apply for a more limited B1 visa with the annotation “B-1 in lieu of H.” These visas may not be used for pleasure travel.

The Customs and Border Patrol agents at Ports of Entry are aware of this provision. If asked at the border, applicants are advised to explain completely their purpose of travel and that they will not be paid from sources based in the United States. Travelers are encouraged to carry a letter from their host company and Indian employer listing the traveler’s duties, length of stay and remuneration plans.

From an article on ComputerWorld :

Although one out of every four international patent applications filed under the Patent Cooperation Treaty are submitted by foreign nationals living in the United States, unless the federal government does something to make it easier for foreigners to obtain green cards or permanent residency, many of those inventors may leave the United States, causing a “reverse brain drain,” concludes a new study. The study, “America’s New Immigrant Entrepreneurs,” written by researchers at Duke, Harvard, and New York universities, was led by Duke adjunct professor Vivek Wadhwa. Wadhwa says the United States is experiencing a brain drain similar to what countries such as India experienced when so many highly educated foreigners came to the U.S., except now they are leaving the country and returning to tech centers in their native countries. Wadhwa says some venture capitalists estimate that 100,000 skilled workers have returned to China and 50,000 have returned to India over the last few years. There are over a million skilled workers and their families waiting for permanent resident visas, but immigration policy mandates that only 8,400 green cards can be issued to China and 8,400 to India every year. Wadhwa suggests increasing the total number of permanent resident visas from 120,000 per year to either 250,000 or 300,000 and removing all per-country limitations until the backlog is cleared. Wadhwa says the H-1B visa creates more problems than it solves by distorting market forces and allowing companies to bring in workers who will work for lower salaries than American workers. He says it should be eliminated in favor of permanent resident visas. Although he also believes the country’s priority should be to encourage American children to study math and science and participate in technical fields, until the nation accomplishes this he says we must rely on foreign nationals to keep the United States competitive.