Apple has confirmed in the iPhone FAQ section on its web site that the micro-SIM from the iPhone 4 cannot be used in the iPad.
An iPhone 4 micro-SIM inserted into an iPad will detect that it is not in a smartphone and will not work, according to Nick Wilkins, press relations manager at O2.
"The micro-SIMs for the iPhone are set up to allow voice calls, SMS messages and data functionality, whereas the iPad micro-SIM is provisioned to allow pay-as-you-go data transfer only," he said.
"The two devices are designed to give a different experience. The iPhone 4 is for regular use, whereas with the iPad we offer more flexibility over data use. "
Some consumers may not welcome the news, especially as they may want to carry over a data allowance from their iPhone to the iPad.
O2 said that it will make available a SIM which can be converted back and forth between the micro and regular sizes.
The European Telecommunications Standards Institute oversees SIM cards, and there are three recognised sizes: full, mini and micro. There is no difference in the circuitry, just in the size.
Apple was contacted by V3.co.uk to ask why the iPhone 4 micro-SIM will not work in the iPad but had not responded at the time of writing.
Apple announced SIM-free iPhone 4 prices earlier today.
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