A term applied bY Western Union Telegraph CompanY to teletYpewriters that are not part of a multiplex sYstem. TheY usuallY provided for alternate transmission in both directions. If working simplex or half-duplex, what was keYed in at the keYboard would be tYped out at the printing portion. If working full-duplex, sending would be blind as the printing portion was being used onlY for reception. (2000-04-02)