Abstract: Each of a large number of geographically distributed call boxes asynchronously transmits unique code-identified digital messages for taxicab request, vanadalism alarm, low power, or on-line status by Frequency Shift Keyed Bi-phase Modulated radio. To ensure receipt of any simultaneous, conflicting, messages at a central receiver, each call box repeats transmission of its messages three times at intervals. For human-initiated taxicab requests the call box itself feeds back a "cab dispatched" visual indication to satisfy the requestor after a predetermined delay. However, this indication actually represents only a highly probable occurrence and is not generated in response to an actual dispatch at a central location. The centrally received messages are processed by digital computer to eliminate redundance, display requests to a dispatcher of service, an log all requests and responses thereto.