Adtran ( ADTN) slashed first-quarter earnings guidance Friday, citing weak bookings. The telecommunications supplier expects to earn 19 cents to 22 cents a share on sales of $106 million to $112 million in the three months to March 31. Adjusted earnings are expected to be 21 cents to 24 cents a share. Analysts surveyed by Thomson First Call were forecasting adjusted earnings of 31 cents a share on sales of $130.1 million. "Our first quarter is normally affected by seasonality with booking rates typically increasing in the latter portion of the period," the company noted. "The increase in bookings activity normally experienced as we progress through the first quarter began later than anticipated, negatively impacting shipments. Overall, we believe our growth drivers remain in place and our outlook for the year has not changed." The stock closed at $27.94 Thursday.