EXHIBIT 12.1 COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES ---------------------------------------------------------------------------------- NINE MONTHS ENDED YEAR ENDED SEPTEMBER 30, DECEMBER 31, --------------------------- ---------------------------------------------------- 1997 1998 1993 1994 1995 1996 1997 ----------- ------------ -------- -------- -------- -------- -------- (In thousands) Ratio of earnings to fixed charges: Earnings (deficiency): Income (loss) from continuing operations before taxes $53,173 $ (4,209) $18,812 $28,343 $38,081 $59,828 $60,278 --------- --------- --------- --------- --------- --------- --------- Fixed Charges: Interest charges 199 1,666 887 3,172 3,188 2,774 293 Interest factor of operating rents 1,524 2,240 738 877 1,240 1,871 2,142 --------- --------- --------- --------- --------- --------- --------- Total fixed charges 1,723 3,906 1,625 4,049 4,428 4,645 2,435 --------- --------- --------- --------- --------- --------- --------- Earnings (deficiency), as adjusted $54,896 $ (303) $20,437 $32,392 $42,509 $64,473 $62,713 ========= ========= ========= ========= ========= ========= ========= Ratio of earnings to fixed charges 31.9x N/A (1) 12.6x 8.0x 9.6x 13.9x 25.8x ========= ========= ========= ========= ========= ========= ========= (1) For the nine months ended September 30, 1998, there was a deficiency of earnings available to cover the fixed charges amounting to $4.2 million. Excluding the charge of $68.2 million for purchased in-process technology associated with the acquisition of Voicetek Corporation, the ratio of earnings to fixed charges for the nine months ended September 30, 1998 would have been 17.4x.