By Neil Hughes

Published: 02:35 PM EST (11:35 AM PST)

Apple on Thursday issued iOS 4.0.1 for the iPhone, improving the accuracy of the handset's signal display strength. It also released iOS 3.2.1 for the iPad to improve Wi-Fi connectivity issues.

Issued Thursday afternoon, Apple said that iOS 4.0.1 includes just one fix, improving "the formula to determine how many bars of signal strength to display." It is available for the iPhone 4, iPhone 3GS, and iPhone 3G.

The iPhone release came a day after Apple released a beta of a different update, iOS 4.1, to developers. That forthcoming update is expected to include a number of fixes that go beyond the reporting of signal strength on the iPhone.

The cosmetic software fix, however, does not address antenna issues that some users have experienced specifically with the iPhone 4 hardware. Apple is expected to reveal its reaction to that issue at a press conference scheduled for 10 a.m. Pacific Time on Friday.

There was no indication that iOS 4.0.1 will address the proximity sensor issue that has affected some iPhone 4 owners. The problem can cause the phone's touchscreen to become active while on a call, causing users to accidentally place a call on hold, end the call, or choose another option on the display.

iOS 3.2.1 for the iPad, according to Apple, includes a number of fixes:

• Improved Wi-Fi connectivity
  
• Fixed an issue that could prevent copy and paste of single-page PDF attachments in Mail
  
• Addressed an issue that could cause video playback to freeze
  
• Improved reliability of video-out when using iPad Dock Connector to VGA Adapter
  
• Added Bing as an option for Safari's search field

While Apple quickly issued an update, as promised, for the iPhone 4 bar issue, the iPad update took more time. Apple had originally revealed that a fix for Wi-Fi issues was forthcoming in May.

A number of users have reported dropped signals and connectivity issues with the iPad when connected to a Wi-Fi wireless network. The IT department at Princeton University said the issue occurred because the iPad would continue to use a network-assigned IP address after it had expired.