The hardware implementation eventually revealed itself as an anti-feature. If one assumed that all the data being read and written was a decimal representation of binary data the system made perfect sense, but if the data was in some other form, more complex assembler language character codes for instance, it ended up simply adding complexity that then had to be turned off. The system was eventually removed when assembler programming became common. It also seriously limited the sorts of devices that could be hooked up, due to the careful tuning of the interface speed.