Textronix Communications, a unit of Beaverton, Oregon-based test equipment provider Tektronix, said today that it has signed a definitive agreement to acquire Arbor Networks, a developer of network security and management products for the carrier market. Financial terms of the buy were not disclosed. Tektronix Communications is based in Plano, Texas. Arbor Networks is located in Chemlsford, Mass, and serves mobile and fixed-line operators, cable and DSL providers, ISPs and others with its products. Tektronix Communications said it expects the deal to close in September.