Apparatuses, methods, and computer programs for displaying information on signs

-Mobile Unit's Controller Main Loop~186

-If receive message from central system~188

-Read message to determine its type~190

-If message is a display-selection message~192

-For each display message identified in display-selection message~194 -If identified display message is part of display-selection message~196

-cause display message to be shown on display~198 -else if identified display message is stored in cache memory~200

-Cause identified display message's data to be read from

memory and shown on identified display~202 -else if the identified display message is a message in a broadcast data stream~204

-cause the data-stream receiver to receive the identified

display message-206

-cause the identified display message to be shown on the mobile unit's display in real time-208 -else send a locator signal indicating mobile unit does not have requested message-210 -if message contains a locator-signal period~212

-set mobile unit's locator-signal period to period specified in signal~214 -if message is a caching message~216

-cache display messages identified in caching message~218 -if message is a locator-signal-period message~220

-set mobile unit's locator-signal period walking were sitting to period specified in signal~222

FIG. 9

-Display-selection message~224

-Header~226

-Mobile Unit ID-228

-1st Display Message ID-230

-2nd Display Message ID-232

-[locator-signal period]~234

FIG. 10

-Display-selection message~224A

-Header~226
-Mobile Unit ID-228
-1st Display Message~236,
-2nd Display Message-236
-[locator-signal period]~234

FIG. 11

-locator signal~240
-header-242
-mobile unit ID-244
-GPS coordinates~246

-ID of display messages currently being shown on each display -248
-Vehicle speed-250

-[missing selected display messages]~252
-[intended destination]~254

FIG. 12

-Mobile Unit's locator-signal daemon~260

-if time since last transmission of a locator signal is equals locator-signal period~261 -transmit a locator signal including~262

FIG. 13

-Mobile Unit's vehicle destination-input daemon-264
-if vehicle destination has been entered~266

-send a wireless locator signal to central system also informing it of the
intended location~268

FIG. 14

-Mobile Unit's speed monitoring daemon~270

-read vehicle speed generated by speed sensor~272

-if vehicle speed or direction of mobile unit has change by more than a certain

amount-274

-vary locator-signal period accordingly~276

FIG. 15

Central System's Locator Signal Response Programming~280
-if receive a locator signal~282

-associate a geographic location with the mobile unit which sent the
signal~284

-determine which geographic zones the location is in~286
-if display messages which locator signal indicates are being shown on mobile
unit are different than those in the last display-selection message sent to the
mobile unit~288

-indicate difference in billing data base~290
-if the mobile unit is in a geographic zone for which different display message
should be shown than those in the locator signal~292

-select the display messages to be displayed by the mobile unit based

on the zone and current time~294

-send a display-selection message to the mobile unit identifying the
selected display messages to be shown on the mobile unit~296
-record zone, time, and display messages associated with display-
selection message in billing data base~298
-record information about the location of the mobile unit derived from its
locator signal in the mobile unit location history data base~300
-if variable frequency locator signals are being used~302

-determine, from locator signal, a distance from the mobile unit to the
boundary of its current geographic zone~304 I
-based on this distance and the speed of the vehicle, calculate the
length of time before the mobile unit is likely to exit its current
geographic zone~306

-based on this length of time, calculate a locator-signal period,
indicating how long it should be before the given mobile unit transmits
each of one or more subsequent locator signal~308
-send a wireless locator-signal-period message to the given mobile unit
containing said locator-signal period~310
-if locator signal includes intended destination-^ 12

-select a subset of a larger set of display messages which are to be

cached by storage in the memory of a given mobile unit as a function of

one or more of said geographic locations which have been associated

with the given mobile unit and of intended location~314

-send a wireless caching message to the given mobile unit informing

the given mobile unit to cache the selected subset of display

messages-316

FIG. 16