SECURITY IN POLICE COMMUNICATIONS CAN BE ACHIEVED WITH SPEECH SCRAMBLERS. TIME DIVISION SCRAMBLING IS A SIMPLE SYSTEM WHICH 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. ADJUSTABLE CODE SETTINGS CAN INSURE THAT CAPTURED MACHINES ARE USELESS. FULLY DIGITAL ENCRYPTION TECHNIQUES CONVERT MESSAGES INTO DIGITAL DATA WHICH ARE THEN TRANSMITTED IN A CODED, QUASI-RANDOM CONTINUOUS STREAM OF BITS. FURTHERMORE, 'VOCODERS' MAY BE ADDED WHICH CONSTRUCT CODES AROUNG THE SPEAKERS' VOCAL MECHANISMS AS THEY PRODUCE VARIOUS SOUNDS. THE RECEIVING UNIT USES THIS CODE TO CONTROL AN ARTIFICIAL VOICE WHICH REPRODUCES THE SOUNDS. DYNAMIC CHANNEL MANAGEMENT CAN HELP CONTROL POLICE V.H.F. CHANNEL OVERLOADING. ONE CHANNEL SERVES AS A MONITOR, AND THE CONTROLLER CAN ASSIGN ANY OTHER CHANNEL TO A USER. THE SYSTEM CAN BE AUTOMATED SO THAT A SIMPLE DIGITAL PROCESSOR INFORMS USERS OF FREE CHANNELS. MOBILE AUTOMATIC RADIO DATA SYSTEMS CAN REDUCE TRANSMITTING TIME BY MORE THAN 99 PERCENT FOR ROUTINE LOCATION AND STATUS REPORTS FROM VEHICLES. A CREW MEMBER TOUCHES A FACIA MOUNTED MAP TO SIGNAL HIS LOCATION, AND HE RECEIVES MESSAGES THROUGH AN ON-BOARD TELEPRINTER. AN AUTOMATIC VEHICLE LOCATION SYSTEM USES DIRECTION AND DISTANCE TRAVELLED SENSORS TO ACTIVATE A GEOGRAPHIC DISPLAY IN THE STATION'S CONTROL ROOM. MANUFACTURERS ARE NOT IDENTIFIED.