Features
This amplitude
discriminator is designed for audio and sub-audio signals
such as extracellular nerve action potentials. For every
waveform peak that appears “within” the window
aperture set by the user, a pulse is generated at the
“Within Window” output. Signals that exceed the upper
level of the window produce a pulse at the “Above
Window” output. A visual indication of the pulses is
provided at each output by the LED display. Both the input
signal and the window aperture settings are visible at the
multiplex port as shown below in the upper trace. By
viewing the input signal as well as the “window”
discriminator levels at the multiplex port provides a
convenient visualization and ease in setting up an
experiment.
Multiplex circuitry
Model 121’s multiplex
circuitry samples input signals and window levels on a
70%/30% basis respectively, minimizing loss of signal
information. The Lower Level control sets the lower
discrimination level, and the Window Aperture control sets
the upper window level with respect to the lower level
setting. This means that changing the lower level setting
has no effect on the window aperture except to displace
the window up or down. It is impossible to set the lower
level higher than the upper level, a feature unique to
Model 121. The pulses from either output (Within Window or
Above Window) are generated by the falling edge of the
analyzed signal as it crosses the preset levels. Because
the logic circuit is not time dependent, Model 121 can be
used to analyze signals of any duration. Ten-turn controls
with dial indicators allow precise setting and direct
reading of the window levels. Enclosure includes a tilt
stand for bench operation. Rack mounting hardware is
optional.
