THE HISTORY OF POLICE RADIO SYSTEMS FROM THEIR INTRODUCTION IN 1923 TO THE PRESENT TWO-TIER SYSTEM UTILIZING POCKET-SIZED, PERSONAL U.H.F. RADIOS AND VEHICLE-MOUNTED V.H.F. SETS IS DESCRIBED. COMMUNICATION BETWEEN CENTRAL AND LOCAL STATIONS IS FACILITATED THROUGH FULLY INTEGRATED, AUTOMATIC MESSAGE SWITCHING SYSTEMS WITH THE CAPABILITY OF STORING MESSAGES AND FORWARDING THEM WHEN RECEIVERS ARE FREE. THE HOME OFFICE'S MOBILE AUTOMATIC EXPERIMENT PROJECT ENVISIONS THE SENDING OF PRINTED MESSAGES TO PATROLMEN WHO ARE ABSENT FROM THEIR VEHICLES, AND AN AUTOMATED VEHICLE LOCATION AND AVAILABILITY SYSTEM WILL INDICATE POSITIONS ON DISPLAYS IN CENTRAL STATIONS. BRITISH INDUSTRY CAN PROVIDE SEVERAL VOICE SCRAMBLERS FOR TRANSMISSION SECURITY. TIME DIVISION SCRAMBLING DIVIDES SPEECH INTO SHORT ELEMENTS AND REARRANGES THEM IN NEW SEQUENCES. THE DESCRAMBLER REVERSES THE PROCESS AND RESTORES THE SPEECH. PSEUDO-RANDOM-CODE SCRAMBLING PROVIDES ADDED SECURITY BY ARRANGING THE SPEECH ELEMENTS INTO NON-REPEATING PATTERNS ACCORDING TO CODES. FULLY DIGITAL ENCRYPTION TECHNIQUES CONVERT MESSAGES INTO DIGITAL DATA WHICH ARE THEN TRANSMITTED IN CODED, QUASI-RANDOM CONTINUOUS STREAMS OF BITS. FURTHERMORE, 'VOCODERS' MAY BE ADDED WHICH CONSTRUCT CODES AROUND THE SPEAKERS' VOCAL MECHANISMS AS THEY PRODUCE VARIOUS SOUNDS. DYNAMIC CHANNEL MANAGEMENT CAN HELP CONTROL POLICE V.H.F. CHANNEL OVERLOADING. MOBILE AUTOMATIC RADIO DATA SYSTEMS CAN REDUCE TRANSMITTING TIME BY MORE THAN 99 PERCENT FOR ROUTINE REPORTS FROM VEHICLES. NAMES OF MANUFACTURERS, APPENDIXES, AND FOOTNOTES ARE NOT INCLUDED. RELATED DOCUMENTS ARE NCJ 65496 AND 65497.