Some Verizon Wireless customers in Bismarck may have been affected by an unidentified source on Tuesday and Wednesday.

Karen Smith, a spokesperson for the cellular phone service provider, said that between roughly 2 p.m. Tuesday and 3 p.m. Wednesday, Verizon Wireless technicians detected an external signal interfering with the frequency the company uses.

"It affected customers being able to make and receive calls," she said.

Smith said what likely caused the problem was a bi-directional amplifier, which boosts the ability of a electronic to receive a signal. These kinds of devices are often used in homes to get better reception on televisions or to boost wireless Internet signals.

The problem is that these amplifiers can interfere with cellular telephone frequencies, Smith said, which is why they recommend they only be used in rural areas.

"It's a fairly frequent occurrence," Smith said. "Just one of those little quirks."

When one of these incidents occurs, Verizon Wireless technicians are able to roughly determine the source by driving around the affected area until it is located.

Smith said that they were very close to determining the exact area, a three-block radius downtown around Seventh Street and Main Avenue, when the interference source suddenly stopped.

(Reach reporter Chris Rosacker at 250-8254 or at chris.rosacker@bismarcktribune.com.)