Millisecond accurate USB response pad with voice key technical specifications
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For the more technically minded, specifications for our millisecond accurate USB response pad with voice key can be seen below. We think it's important for you to have full confidence in our USB response pad and voice key when using them in your psychology experiments.

We have taken the decision to publish full technical and timing specifications for our USB response pads and voice keys as all too often the equipment you use on a daily basis is of unknown quality.

In our view, if other vendors do not publish specifications for their hardware or software you should not be using it!



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Technical specifications

Physical specifications *Nominal accuracy
  • Carbon fibre effect plastic enclosure (202mm x 137mm x 35mm LWH)
  • 4x Japanese Seimitsu PS 14 GN 30mm dia buttons, overall dia 34.5mm (certified for min 1,000,000 presses)
  • 4x Active Switch Closures (9-way D) to short out external push-to-make buttons on external equipment
  • Depending on model up to 8x unique TTL markers rather than ASC port (one per button, 9-way D)
  • 1x 3.5mm stereo socket for the BBTK headset with condenser microphone
  • 1x adjustable potentiometer to set the activation threshold or sensitivity for the voice key, i.e. crossing threshold -- one word typically triggers one keystroke
  • 1x 2.5mm stereo socket for +5V TTL event marker on any button down or voice key activation
  • 4x 3.5mm mono sockets for external push-to-make button input
  • Full-Speed USB 2.0 (USB 3.0 compatible)
  • 4x unique +5V TTL event markers for use with The Black Box Toolkit v2 (9-way D)
  • Appears to the host PC/Mac/Linux system as a standard HID keyboard (no drivers required)
  • Anti-ghosting technology means that up to 6 buttons can be held down and released in any order whilst being correctly reported to the host operating system – meets full USB HID keyboard specifications (this also includes a voice key activation)
  • Fully updatable firmware – 32K flash RAM (100,000 Erase/Write Cycles)
  • In USB response pad mode checks for a button press 45,450 times a second (45.5kHz sampling rate)
  • Voice key input (from silence) to TTL event marker typically under 5 ms dependent on threshold setting (see screen grabs below)
  • Voice key silence window 250ms – window during which waveform should be below threshold to signal an off
  • In Black Box response pad mode checks for a button press 221,000 times a second (221kHz sampling rate)
  • Typical time to recognise a button press 10 millionths of a second (10.20µs)
  • Typical time to transmit keystroke(s) to PC after detecting a button down or voice key activation 60-87 millionths of a second (60-87µs) – status of up to 6 buttons/keys from 9 (8 buttons/1 voice key), transmitted on first available USB packet
  • Typical time to recognize a button up 75 millionths of a second (75µs)
  • 2.5mm socket +5V TTL pulse width 50ms (interrupt driven timer)
  • 4x ASC's 0.4ms inherent delay due to use of Solid State Relays (SSR) to protect your equipment
  • 4x BBTK +5V TTL signal matches button down onset, duration and offset
  • 25ms button up debounce (a button has to be cleanly up for 25ms before a key up signal is sent to the PC)#

#This can add 25ms to key down durations -- onsets or RT's are unaffected as these are sent to the host PC immediately. ALL standard keyboards and other response boxes typically have longer debouncing periods. In addition operating systems have a set key repeat rate during which they don't accept key presses faster than a certain rate.

Remember although our USB response pads are millisecond accurate and help reduce RT variability in your experiments they can't automatically correct for any mistimings that are inherent within the experiment generator you use (key features).


In order to validate our claims for accuracy we have tested the shipping electronics and firmware thoroughly. Below are a series of screen grabs from one of our Tektronix oscilloscopes.

   
Silence (1) to voice key activation and TTL event marker (2) typically under 5ms (activation or crossing threshold dependent on setting and shape of waveform) Voice key silence window 250ms (window during which waveform should be below threshold to signal an off is dependent on waveform as shown with the jittery tail end above) -- one word typically triggers one keystroke
   
   
USB mode sampling rate, i.e. how many times a second button and voice key status is checked BBTK mode sampling rate, i.e. how many times a second button status is checked
   
   
Physical button down (1) to TTL event marker (2) scale 5µs Physical button down (1) to USB keystroke sent on first available USB packet to PC (2) mean 65µs
   
Physical button up (1) to TTL event marker (2) TTL pulse width