<PAGE>
Exhibit 12.1
TranSwitch Corporation and Subsidiaries
Computation of Ratio of Earnings to Fixed Charges
(Unaudited)
(Dollars in thousands)
<TABLE>
<CAPTION>
Nine months ended
September 30, Year Ended December 31,
--------------------- ------------------------
2000 1999 1999 1998 1997(b) 1996(b) 1995(b)
------- ------ ------- ------ ----------- ----------- -----------
<S> <C> <C> <C> <C> <C> <C> <C>
Earnings:
Income (loss) before $39,269 $6,078 $22,522 $6,544 $(1,621) $(9,663) $(1,685)
income taxes
Add:
Fixed Charges as 1,822 270 380 395 439 264 224
described below ------- ------ ------- ------ ------- ------- -------
$41,091 $6,348 $22,902 $6,939 $(1,182) $(9,399) $(1,461)
======= ====== ======= ====== ======= ======= =======
Fixed Charges:
Interest Expense $ 1,272 $ 27 $ 35 $ 143 $ 208 $ 129 $ 47
Amortization of $ 268 - - - - - -
costs related to
indebtedness
Estimated interest 282 243 345 252 231 135 177
factor in rent ------- ------ ------- ------ ------- ------- -------
expense (a)
$ 1,822 $ 270 $ 380 $ 395 $ 439 $ 264 $ 224
======= ====== ======= ====== ======= ======= =======
Ratio of Earnings to 22.6 23.5 60.3 17.6 (2.7) (35.6) (6.5)
Fixed Charges ======= ====== ======= ====== ======= ======= =======
</TABLE>
(a) The estimated interest factor in rent expense represents one third of
rental expense.
(b) The deficiency in earnings in relation to fixed charges for the year ended
December 31, 1997, 1996 and 1995 is $2.1 million, $9.9 million and $1.9
million, respectively.
