Shares of Globalstar Telecommunications Ltd. plunged 50 percent on Tuesday after the satellite telephone operator said it would stop paying debt holders so it can save cash to fund its operations into 2002. Globalstar, which was founded by Loral Space & Communications Ltd. and Qualcomm Inc., said it would save $400 million in 2001 by suspending payments on its funded debt, including its credit facility, vendor financing agreements and senior notes. The company said it will also halt dividend payments on its preferred stock. Shares of Globalstar were 29/32 lower at $1 at midday on Nasdaq, on volume of 10.1 million shares, after dipping as low as 15/16.