Psion has issued a warning to owners of its Series 7 handheld computers about a potential fault. According to the company's Web site, the external power supply may be faulty on certain devices. "A potential failure with the Power Supply Adapter supplied with the Series 7 product has been identified and under exceptional circumstances may malfunction," it said. Only certain external power supply units are affected. Users can find out if their kit is likely to be faulty by entering the batch number here. ®