Motorola Corporation

Richard E Murray

Masaru Tokiyama

Kevin M Laird

Steven T Barrett

James M O'Connor

William H Robertson, Jr

William C Phelps, Iii

Thomas J Zuiss

Mobile radio

Control head for a mobile radio

Briefly, according to the invention, the interface device comprises matching device (20 and 22) for coupling a duplex information signal (21 and 23) to a simplex or a duplex radio (6) which provides a corresponding information signal (27) acknowledged by the half duplex or full duplex radio (6). Additionally, a signal detecting means (24) determines a desired signal strength and controls an interrupt signal (32). A means for sending (26) the interrupt signal (32) to the radio (6) sends the interrupt signal once the signal detecting means detects the desired signal strength. Finally, the interface device of the present invention comprises a means for sending (26) the corresponding information (27) once the interrupt signal is sent.

Facsimile interface device for radios

A radio (100) transmits and receives encrypted signals having unencrypted key identifiers, allowing other radios having the corresponding key identifiers and encryption keys to communicate with radio (100). Prior to transmitting an encrypted message, radio (100) selects a unique key identifier automatically and uses the corresponding encryption key to encrypt the message that will be transmitted. Radio (100) transmits the key identifier in an unencrypted format with the encrypted message in order to allow other radios to determine the encryption key used in encrypting the message. When receiving an encrypted message, radio (100) uses the predetermined process stored in the radio (100) to properly select the proper encryption key for use in decrypting the incoming message.

Dynamic encryption key selection for encrypted radio transmissions

A trunked communication system (400) transmits and receives encrypted signals over the system control channel (402). The trunked system (b 400) includes a plurality of radios (300) which can communicate with the communication system via control channel (402). By using control information signals and system information signals radios (300) can determine if it they are capable of decrypting the encrypted control information signals sent over the control channel (402). This is done by first determining if the encryption identification field found in the unencrypted system information signal matches an encryption identification field found in radio (300). If a match is found between the radio's encryption identification and the encryption identification field in the system identification signal radio (300) loads the encryption into the encryption circuitry in order to successfully decrypt the control information signals.

Encrypted trunked control channel system

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Coral Springs, FL, United States of America

Richard E Murray