IFSP (German: Interface sternförmig parallel, Russian: Интерфейс радиальный параллельный (ИРПР)), radial parallel interface, was a parallel interface similar to Centronics but incompatible, as it had different signal polarities and handshake protocol. Used in printers and computers manufactured in Comecon.
All printer input signal lines were pulled up to +5V by 220 Ohm resistor, and pulled down to ground by 330 Ohm resistor. This allowed usage of longer cables comparing to Centronics, but overloaded most usual Centronics adapters.
Some devices allowed switching between IFSP and Centronics modes, i.e. Robotron 6319—6329 were manufactured with interchangeable interface modules, allowed usage of IFSP, IFSS and Centronics.
Read more about IFSP: Signal Description, See Also