Abstract: A digitally controller radio transceiver includes a housing including a front cover provided with a display port; a main controller board mounted within the housing; an optional display board attached to an interior surface of the front cover adjacent said display port, said display board electrically connected to said main controller board by a pressure fit connection; a removable display escutcheon plate mounted on an exterior surface of the cover, overlying the display port; and fastening means extending through the cover and connecting the display board to the display escutcheon plate. Removal or omission of the display board is automatically sensed by the radio transceiver's internal microprocessor which operates accordingly. In one embodiment the transceiver program store may be loaded via an external connector to customize the microprocessor instruction code for the presence or absence of a display.

Abstract: Time delay compensation is inserted into a digital signal processing channel having compressed bandwidth portions at a point where the bandwidth is compressed. Since a smaller number of bits per unit of information is present at such a point, this reduces the number of bits which must be buffered to achieve a given amount of time delay compensation. For example, in a subband coder/decoder using a non-symmetrical QMF filter tree, the necessary time delay compensation in the various subband channels is effected subsequent to a digital bandwidth compression encoding step on the transmitter side. On the receiver side, similar time compensation may be provided in the subband channels prior to a digital bandwidth expansion decoding step. By implementing the necessary digital time delay compensation at a point in the system where the signals are bandwidth compressed to a maximum degree (i.e.

Abstract: Different digital radio transceiver front panel escutcheon plate assemblies are provided for different optional transceiver configurations. A digital signal controller which is part of the main transceiver circuitry is capable of performing any of various basic and option functions under control of program control instructions stored in an associated non-volatile memory. Subsets of those features are selectively disabled by irreversibly modifying the transceiver unit from the outside of the unit (e.g., by cutting certain PC board pathways through holes provided in the transceiver unit front panel). The controller enables (executes) portions of the program control instructions stored in its associated non-volatile memory and disables (does not execute) other portions of the stored program control instructions in response to detection of continuity/discontinuity over those certain pathways.

Abstract: Hybrid subband coding and decoding (using different encloding/decoding algorithms in at least one subband channel) and subband time delay compensation at a point of maximum digital bandwidth compression are effected so as to reduce required DSP on-chip memory requirements. At the same time a special digital signal format is employed so as to provide enhanced data frame synchronization, enhanced cryptographic synchronization and selective signalling ability within a cryptographic digital signal transceiver. The ability to successfully accomplish late entry (or to re-establish synchronization once lost) into an ongoing received message is provided.

Abstract: Method and apparatus are disclosed for transceiving digital control and cryptographically encoded data signals in a unique format. The format includes frame synchronization, cryptographic synchronization and selective signalling (addressing) information both in a preamble portion to an entire message and recurrently at regular intervals throughout a message of encrypted digital voice signals. This arrangement permits successful late entry and/or synchronization recovery (both frame and cryptographic synchronization recovery) in an addressable selective signalling type of private radio communication system even if such synchronization is never acquired from the preamble (e.g. because of a long radio transmission channel fade or the like) or in the event such synchronization is temporarily lost after the preamble has already occurred.