A compatible analog channel unit for a digital cellular telephone system services both analog and digital mode subscribers on the same system hardware. The analog channel unit which may be configured by the service provider to permit easy upgrading of service during the life of the equipment without additional capital expense to the service provider. All analog system functions required of an analog cellular base station are provided in firmware and executed on commercial digital signal processors (DSPs). The same DSPs, when down-loaded with different firmware, perform TDM/TDMA related functions as required of a digital cellular base station. A system operator can configure channel units from a remote location by simply downloading the appropriate firmware. The channel unit firmware, whether analog or digital, is downloaded into the system hardware according to the assigned mode. This permits dynamic channel allocation according to system requirements. Since this is a digital system, special features may be added by simply revising the system firmware. This means future product enhancements may be provided without affecting the system hardware.