Throughput is reduced by errors. If the raw error rate increases to 3% the link will be blocked all the time with retransmissions. Each transmitted cycle of 28 bits has a likely chance of an error in these conditions. An eight character repeat cycle has twice the impact. At 1% raw errors the throughput for the 4 character cycle system is about 80%. On real equipment, an efficiency meter may indicate how good the throughput is. Alphabet The alphabet used in the ARQ-M protocol is based on the CCITT Telegraph Alphabet No. 2 more commonly known as Baudot. This alphabet has five bits, and therefore has 25 or 32 different possible symbols. It uses letters shift and figures shifts to select different sets of characters similar to a typewriter. The ARQ-M alphabet being synchronous always has to send data and does not have gaps between characters. It does not include start and stop bits that would be used in asynchronous transmissions and so saves on those two bits per character. In asynchronous transmissions a steady stop signal indicates that there is nothing to send. A prolonged start signal can be used for signalling, for example to select a destination for a telex connection. The ARQ-M characters are remapped to a seven bit system so that there are always three bits on and four bits off. The ARQ code is a Moore code, which can detect the modification of any single bit. This alphabet is CCITT Telegraph Alphabet No. 3 aka TOR No. 3. This differs from the alphabet used in the ARQ-E single channel system. Three additional control signals are added to the 32 from the Baudot set. Out of 128 seven bit characters there are 35 that have three one bits set, so allowing for the 32 Baudot and three control codes to just be accommodated. The extra control characters are RQ, meaning request repeat, α meaning constant space condition, which may indicate the end of a connection (break signal) or be used to signal information, such as a number to connect to, and the β character, meaning constant mark condition, used when there is nothing to send. The RQ signal is also called Signal Roman one and may be designated "I". The number of one bits is checked by the receiver to tell if an error has occurred in the transmission of the character. There should be three