Validation method for transmitting data in a two-way audience response teaching system

In wireless remote units for transmission of audience response data to a central processor, a communications method comprising the steps of:

• retrieving remote ID data of at least 8 bits from remote unit memory;
• retrieving participant data of at least 3 bits from remote unit memory;
• forming a set of at least 2 transmission data groups, each of at least 4 bits from all retrieved bits of data in a manner that prevents sequences of consecutive bits in retrieved data from appearing as a transmission data group;
• including at least one marker bit in each transmission data group;
• forming a checksum data group of at least 2 bits by binary calculation from said set of at least 2 transmission data groups;
• forming a first data packet from a series said transmission data groups and said checksum data group;
• transmitting said first data packet;
• forming a second set of at least 2 transmission data groups, each of at least 4 bits, from all retrieved bits of data in a manner that prevents sequences of consecutive bits in retrieved data from appearing as a transmission data group, said second set of transmission data groups being formed in a different manner than the first set of transmission data groups thereby preventing substantial duplication of bit patterns therein;
• if said first set of transmission data groups was not set to the inverse of the retrieved data, then setting said second set of transmission groups to the inverse of the retrieved data;
• including at least one marker bit in each transmission data group;
• forming a checksum data group of at least 2 bits by binary calculation from said second set of at least 2 transmission data groups;
• forming a second data packet from a series said transmission data groups and said checksum data group;
• transmitting said second data packet promptly following said first data packet.