Kansas City Standard
Tape Data Recovery - Kansas City Standard
The Kansas City Standard (KCS), also known as Byte standard or Computer Users’ Tape Standard (CUTS), was a format for storing digital data on ordinary compact audio cassette drives. KCS was developed in 1975 at a symposium sponsored by Byte magazine in Kansas City, Missouri.
KCS uses asynchronous serial data. The cassette uses an interface similar to a modem connected to a serial port. The 1s and 0s from the serial port are encoded using audio frequency shift keying (AFSK) such that a ‘0′ bit is represented as four cycles of a 1200 Hz sine wave, and a ‘1′ bit as eight cycles of 2400 Hz. This results in a data rate of 300 baud.
Each frame starts with one start bit (a ‘0’) followed by eight data bits, further followed by two stop bits (‘1’s). Thus each frame consists of 11 bits, for a data rate of 27 bytes per second.
Examples of computers using Kansas City Standard include MITS Altair 8800, PT SOL-20, Ohio Scientific C1P/Superboard II, Compukit UK101m, Motorola MEK D1 6800 microcomputer board, Nascom, and Acorn Atom.
The 1200 baud variation of CUTS was implemented by Acorn Computers in their BBC Micro and Acorn Electron microcomputers. In this standards, a , ‘0′ bit was represented as one cycle of a 1200 Hz sine wave and a ‘1′ bit as two cycles of a 2400 Hz wave. Standard encoding includes a ‘0′ start bit and ‘1′ stop bit around every 8 bit piece of information. This resulted in an effective data rate of 960 bits per second.
