Transmission The seven bits resulting are converted from parallel to serial, sending the left-most element first, and then modulated onto a radio carrier using frequency-shift keying. Standard baud rates are 48, 64, 72, 86, 96, 144, and 192 baud. Repeat request When an error is detected in a character received, then an RQ symbol is sent, along with a repetition of the last characters in the cycle. When an RQ is received, then an RQ is sent along with repeated characters starting from the one flagged as having a problem. The repeated characters would be three in the four character cycle, and seven in the eight character cycle. For the five character cycle, three characters are repeated after two RQ characters. For encrypted characters streams, it is very important to get the position in the sequence precisely correct, and it cannot afford to make a mistake with repeated data. Variants Different variants of ARQ-E include ARQ-E3 which uses a different alphabet, ITA3 as in ARQ-M. ARQ-E3 can also be called CCIR 519. ITU standard F.519 introduces this as a variant of ARQ-M, but with one channel. Standard bit rates are 48, 72 and 96 baud. ARQ-N is similar to ARQ-E but there is no marking pattern. Monitoring Software is available for professionals and hobbyists to receive and decode utility transmissions that use ARQ-E. Software includes go2MONIOR which can handle the variants and multipsk, the Rohde & Schwarz GX401DC, the Hoka Code2-32P, and Code200-32, Wavecom, the WiNRADiO Universal FSK Decoder,. Early software included Radioraft. References Quantized radio modulation modes