Abstract: A shock isolator (30) is provided within the housing (38) of a selective call receiver to substantially increase the natural frequency of vibration of the housing (38) and the printed circuit boards (54, 56) within the housing. The shock isolator (30) is a body of elastomeric material, preferably butyl rubber, which has component receiving apertures (32) molded therein for receiving the components (46, 48, 50) on the printed circuit board while at the same time contacting the printed circuit board. The butyl rubber has a damping of at least 25% (preferably 50%) and a Durometer of between 50 and 70 type A (preferably 60).

Abstract: A communication system (100) has at least one base site (204) which includes a plurality of transceivers (110A-C) operating on a plurality of communication channels for communicating to at least one of a plurality of communicators (108). The at least one base site (204) comprises a generator (210) generating a plurality of interference signals according to a predetermined pattern on a subset of the plurality of communication channels. A processor (208) initiating and terminating communication between the base site (204) and the at least one communicator (108) on a selected communication channel substantially free of interference signals. The processor (208) further determines the communication channel being selected, and determines whether to change the predetermined pattern of the plurality of interference signals.