<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
       
<S>                             <C>                     <C>                     <C>
<PERIOD-TYPE>                   3-MOS                   6-MOS                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1997             DEC-31-1997             DEC-31-1997
<PERIOD-START>                             JAN-01-1997             APR-01-1997             JUL-01-1997
<PERIOD-END>                               MAR-31-1997             JUN-30-1997             SEP-30-1997
<CASH>                                         864,000               1,349,000                 374,000
<SECURITIES>                                10,762,000               9,398,000               3,240,000
<RECEIVABLES>                                7,168,000               6,669,000              10,667,000
<ALLOWANCES>                                 (620,000)               (665,000)               (733,000)
<INVENTORY>                                    213,000                 155,000                 268,000
<CURRENT-ASSETS>                            18,425,000              17,568,000              14,270,000
<PP&E>                                      17,255,000              17,352,000              24,081,000
<DEPRECIATION>                            (11,130,000)            (11,904,000)            (16,756,000)
<TOTAL-ASSETS>                              26,729,000              25,354,000              29,085,000
<CURRENT-LIABILITIES>                        5,636,000               5,083,000               7,666,000
<BONDS>                                              0                       0                       0
<PREFERRED-MANDATORY>                                0                       0                       0
<PREFERRED>                                          0                       0                       0
<COMMON>                                    19,056,000              19,056,000              18,711,000
<OTHER-SE>                                           0                       0                       0
<TOTAL-LIABILITY-AND-EQUITY>                26,729,000              25,354,000              29,085,000
<SALES>                                      8,487,000              17,298,000              28,546,000
<TOTAL-REVENUES>                             8,487,000              17,298,000              28,546,000
<CGS>                                        5,072,000              10,417,000              17,513,000
<TOTAL-COSTS>                                5,072,000              10,417,000              17,513,000
<OTHER-EXPENSES>                             2,151,000               4,236,000               6,752,000
<LOSS-PROVISION>                                     0                       0                       0
<INTEREST-EXPENSE>                             119,000                 165,000                 239,000
<INCOME-PRETAX>                              1,196,000               2,631,000               4,247,000
<INCOME-TAX>                                   375,000                 942,000               1,606,000
<INCOME-CONTINUING>                            821,000               1,689,000               2,641,000
<DISCONTINUED>                                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0
<CHANGES>                                            0                       0                       0
<NET-INCOME>                                   821,000               1,689,000               2,641,000
<EPS-PRIMARY>                                     0.11                    0.20                    0.30
<EPS-DILUTED>                                     0.11                    0.20                    0.30
        

</TABLE>