DATA INTERFACE UNIT FOR INSURING THE ERROR FREE TRANSMISSION OF FIXED-LENGTH DATA SETS WHICH ARE TRANSMITTED REPEATEDLY

• US 3,772,649 A
• Filed: 02/17/1972
• Issued: 11/13/1973
• Est. Priority Date: 03/02/1970
• Status: Expired due to Term

• Current Assignee: Carl M. Solar, Donald E. Haselwood
• Original Assignee: Carl M. Solar, Donald E. Haselwood
• Inventors: Haselwood, Donald E., Solar, Carl M.
• Primary Examiner(s): Atkinson, Charles E.
• Assistant Examiner(s): Malzahn, David H.
• Application Number:
  US05/227,060
• Time in Patent Office: 635 Days
• Field of Search: 340/146.1BA 178/23A
• US Class Current: 714/822
• CPC Class Codes: H04H 60/32 Arrangements for monitoring conditions of receiving stations, e.g. malfunction or breakdown of receiving stations
• CPC Class Codes: H04H 60/41 for identifying broadcast space, i.e. broadcast channels, broadcast stations or broadcast areas
• CPC Class Codes: H04H 60/94 Telephonic networks for accessing the Internet H04H60/84

Abstract

A data interface unit is designed to receive fixed-length data sets which are transmitted repeatedly and which differ from one another only in the reversal of a single data bit between successive transmissions. The data interface unit stores all the bits comprising a first transmitted data set and then compares each of the data bits in the set to the corresponding bit in a subsequently transmitted data set. When a first disagreement between transmitted data bits is found, that disagreement is assumed to be the bit that was reversed in sign and is also assumed to be the start of the data. If all of the bits save that one bit are the same during both transmissions, then an errorfree transmission is assumed to have occurred and the data set is accepted. However, if two or more data-bit positions are found to disagree, then the transmission is known to contain at least some errors. The data storage and comparison process is then repeated using subsequent transmissions of the data set. This data interface unit is particularly suitable for collecting data from remote locations over conventional telephone lines with the assistance of automatic dialing equipment. The preferred embodiment of the invention is designed for use in carrying out surveys of the listening habits of television viewers.

Claims

1. A data interface unit for error checking and organizing a signal that is transmitted repetitively, said data interface unit comprising:

a serial memory with the capacity to store an entire transmission of the signal, said memory having an input into which the signal is fed and having an output;

a counter;

means for advancing said counter in synchronism with the flow of data bits into the serial memory;

a comparator having two inputs, one connected to the serial memory output and the other receiving the incoming signal, and having an output connected to said counter for resetting said counter whenever the two inputs do not match; and

means connecting to said counter and responsive to said counter reaching a predetermined count for signalling that the serial memory contains an organized, error-free data set.

2. A data interface unit in accordance with claim 1 wherein the signalling means comprises a bistable circuit which changes its state when the counter reaches the predetermined count, said bistable circuit generating a ready signal, and wherein the data interface unit includes recirculation gates connecting the memory output to the memory input and enabled by the ready signal.

3. A machine-implemented method for performing error checks upon and for locating the first data bit in a multi-bit data set that is continuously and repeatedly transmitted as a signal and that contains one data bit whose sign is reversed between successive transmissions, said method comprising the steps of:

recovering from said signal a first group of sequentially-transmitted data bits equal in number to the number of bits in the multi-bit data set;

recovering from said signal a second group of sequentially-transmitted data bits equal in number to the number of bits in the multi-bit data set and appearing in said signal immediately following the appearance of said first group of data bits within said signal;

comparing each data bit in said first group with a correspondingly-positioned data bit in said second group;

preserving a record of the group-relative location of the first data bit in the first group which disagrees with its counterpart in the second group;

presenting either group as an accurate transmission of the data set and presenting said record as an indicator of where within the group the first data bit in the data set is located, but only if no more than one data bit is found in the first group which disagrees with its counterpart in the second group; and

repeating all of the above steps using different first and second groups as many times as is necessary to locate a pair of groups in which only one data bit in the first group disagrees with its counterpart in the second group.