Apple Inc.’s tablet may have to repeat the iPhone’s breakthrough success or risk going the way of personal digital assistants and so-called third devices — products that lack the appeal of phones or personal computers.

The Cupertino, California-based company sent out invitations yesterday to an event on Jan. 27, asking reporters to “Come see our latest creation.” apple is planning to unveil a tablet computer that will probably go on sale in March, a person familiar with the matter said earlier this month.

Consumers haven’t embraced the idea of carrying around a third device in addition to their laptop and mobile phone, said ken dulaney, an analyst at stamford, Connecticut-based Gartner Inc. Tablet computers, also known as slates, account for less than 1 percent of the PC market even though they have been available since the 1990s.

“They buy a large device when they want to get serious, and they buy something that will fit in their pocket,” he said. “Everything that’s in between has turned out to be a temporary category.”

In 2009, pc makers sold 122,000 slate computers — devices without keyboards — according to Framingham, Massachusetts- based research firm idc. That number will increase by 49,000 this year, idc said. Computer companies such as Hewlett-Packard Co. also sell convertible laptops that have hinged, rotating screens that fold over a keyboard. About 965,000 convertible computers were sold last year, idc said.

Earnings Boost

Apple fell $3.50 to $205.93 on Jan. 15 in Nasdaq Stock Market trading. The shares, which more than doubled last year, closed at a record $214.38 on Jan. 5. U.S. markets were closed yesterday for the Martin Luther King Jr. holiday.

Steve Dowling, an apple spokesman, declined to comment on the Jan. 27 event.

If apple sells 3 million tablets for $750 each in the first year, the devices may boost earnings by 21 cents a share, toni sacconaghi, an analyst with Sanford C. Bernstein & Co. in new york, said in a note last week. That estimate includes lost sales of Apple’s notebooks and iPod Touch as a result of the tablet debut.

At $750, the product would be priced between the $399 top- of-the-line iPod Touch and the $999 entry-level macbook notebook, Sacconaghi said.

Apple isn’t alone in creating devices that combine the functions of phones and computers: Hewlett-Packard and dell inc. showed tablet designs at the consumer electronics show in las vegas this month. Still, products that serve as a halfway point between phones and computers may not catch on, said Motorola Inc. Chief Executive Officer Sanjay Jha.

IPhone Effect

“My strong point of view is that if it doesn’t fit in your pocket, you don’t take it to dinner with you, and therefore the usability of that device and the volume is meaningfully lower,” Jha said in an interview this month. “A lot of very smart people have different views. But I am not sure that the middle point is the right answer.”

Apple CEO steve jobs has overcome skepticism before. The 2007 introduction of the iphone removed any doubts that consumers would use phones to access the Internet, said Intel Corp. executive Eric Kim.

“Smartphones had the Internet and browsers for many years, but nobody got it right until apple delivered the iphone,” said Kim, who heads a business at Intel that develops consumer- electronics chips. “After that, the rest was history.”

Apple has sold more than 33 million iPhones since the device first went on sale in June 2007.

Apple Newton

Apple’s record in popularizing new product categories isn’t perfect. Its Newton PDA failed to win over customers in the 1990s. Palm Inc. had more success with its version of the PDA, only to lose out later to smartphones.

In addition to surfing the Web, Apple’s tablet may display books, textbooks, magazine stories and news reports — with links to related content such as photos, video and author interviews, said Kathryn Huberty, an analyst with morgan stanley in new york.

Apple may have signed up a large number of print publishers to offer content on the tablet, Sacconaghi said. HarperCollins Publishers, a unit of News Corp., is in talks with apple to make electronic books available on the device, the Wall Street Journal reported yesterday, citing people familiar with the matter. Erin Crum, a spokeswoman for HarperCollins, declined to comment.

New York Times Co. may strike a partnership with apple as part of its strategy to charge for stories, new york magazine reported on Jan. 17. Diane McNulty, a spokeswoman for the newspaper company, said it will announce its decision on whether to charge for Internet content when it has “crafted the best possible business approach.”

Tablet computers have fallen short in the past because companies haven’t produced custom software or content for the devices, said David Daoud, an idc analyst.

“I suspect if apple gets into that market, the story will be around user experience, not from a hardware perspective only,” Daoud said. The tablet idea hasn’t had that kind of support in the past, he said. “No one championed that product.”