Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of ADTRAN (NASDAQ:ADTN), a provider of networking and communications equipment, slumped on Wednesday after the company reported largely disappointing earnings. By 2:15 Wednesday afternoon, the stock was down about 9%.

So what: ADTRAN's revenue declined by 2.8% year-over-year to $142.8 million during the first quarter, about $3 million shy of analyst estimates. Currency fluctuations were a major driver of this poor revenue performance, as was the cancellation of a program involving Tier 1 carriers that was expected to begin during the first quarter.

ADTRAN did manage to beat analyst estimates for non-GAAP EPS, although profits plunged compared to the same quarter in 2014. ADTRAN reported non-GAAP EPS of $0.10, two cents better than analyst expectations but well below the $0.21 reported during the first quarter of 2014. On a GAAP basis, ADTRAN's EPS declined by nearly two-thirds year-over-year to just $0.06.

Now what: ADTRAN had a difficult quarter, and the market punished the stock as a result. Even after the decline in the stock price, shares still trade at a P/E ratio of about 21, based on earnings from 2014. While analysts are expecting substantial earnings growth going forward, nearly 25% annually for the next five years, that may be far too optimistic in light of the difficulties the company is currently experiencing.