mailing proxy materials to ADT Ltd. shareholders in its $3.5 billion hostile bid to acquire the seller of home-security systems.

Western Resources also said it will hold a special shareholders meeting on April 24 in Topeka, Kansas, to vote on the acquisition. Shareholders of record on March 20 will be able to vote on the acquisition.

In December, Western Resources said it would acquire ADT. Western Resources already owns 27 percent of Bermuda-based ADT, and it wants to buy the rest to gain access to about 1.7 million customers in the US.

Topeka, Kansas-based Western last week filed an amended legal complaint in federal court challenging ADT's recent revision to its "poison pill'' anti-takeover defence.

ADT bolstered its shareholder rights plan the day before it rejected Western Resources' bid earlier this month, according to a Securities and Exchange Commission filing.

Western, the parent company of two Kansas utilities, is trying to take over ADT, the largest provider of electronic security systems in the US, by replacing the board with two of its own executives.

ADT shareholders were scheduled to vote July 8 on Western Resource's plan to replace the ADT board.