1. Field of the Invention
This invention relates generally to remote communication systems and more particularly to data communication receivers and apparatus for use in such systems to compensate for the inherent message delays which occur in the system communication lines and equipment transmitting messages to the receivers.
2. Description of the Prior Art
There are many types of automatic remote communication systems which utilize a computer or control center to communicate with several remote terminals. In large systems, this communication is generally done over communication lines which interconnect the control center to the remote terminals via some type of control or distribution unit.
In some types of systems, such as utility company remote automatic meter reading systems, the remote terminals are responsive to commands sent out by the control center to send messages or meter data back to the control center.
In the aforementioned systems, it is sometimes desirable to collect vast amounts of data in a short period of time. One way to accomplish this collection of data, is to command several terminals to transmit their data simultaneously to the control center. It has been found, however, that the simultaneous transmission of data frequently results in the loss of message information or data. This loss is due in large part to the inherent system delays caused by different turn around delays in the terminal units and the lengthy distribution of terminal units along the communication line or lines interconnecting the terminal units to control unit, which causes the messages to arrive at the control unit receivers at different times.
If the messages from the terminal units do not all arrive at the receivers of the control unit at the same time and if those messages are transferred to the control center based on timing derived from the first received message, it is possible to lose some of the data in the later received messages.
Thus, it can be seen that a need exists for an improved receiver and transfer apparatus for use in communication systems which affords the advantages of compensating for inherent system message delays to prevent the loss of message data.
The system disclosed herein, which makes use of the present invention, is also disclosed in U.S. patent application Ser. No. 653,859, filed Jan. 30, 1976, entitled "Automatic Remote Meter Reading and Control System" and patent application entitled "Meter Terminal Unit For Use In Automatic Remote Meter Reading and Control System", filed concurrently herewith both assigned to the same assignee.