GPI-16 – General Purpose Input Module The GPI-16 interfaces 16 general purpose logic inputs to users PC COM or USB port.
GPI-24 – 24 General Purpose Input Interface Discontinued. Please see the GPI-16. or Discontinued. Please see the GPI/O-32+2.
HPA-4 Plus – 4 Channel Headphone Amplifier with Cue Discontinued. There is no replacement for the HPA-4 Plus at this time.