E-1231
The equalizer shall contain 28 filters on ISO center frequencies from 31.5 Hz to 16k Hz. Each
filter section shall provide up to 12 dB of cut and boost at the center frequency, with linear slide
control operation and a graphic display of the equalization curve. The filters shall be minimum
phase type. The equalizer shall contain high pass and low pass filters having the following
characteristics: Highpass-12 dB/octave with –3 dB point continually adjustable from 15 to 300 Hz,
and Low pass switchable –12 dB or –6 dB with –3 dB point continuously adjustable from 2.5k to
30k Hz. A Filter In/Out switch shall be provided to remove both the high- and low pass sections
from the signal path. The equalizer shall be provided with an EQ bypass switch to remove all
equalizer and end cut filters from the signal chain, with an LED indicator showing status. The
input circuit shall be electronically balanced and shall accept either balanced or unbalanced
sources. The balanced input shall have 10k ohms impedance. The output circuit shall be
electronically balanced and capable of driving a load of 600 ohms or higher. The unit shall accept
optional input and output transformers which shall be internally installed with plug-in connectors.
The unit shall contain a relay circuit which bypasses all internal electronics in the event of power
failure. An output muting function shall be provided to suppress turn-on and turn-off transients.
The unit shall allow for the removal of an external connecting link to separate the signal and the
chassis grounds. Barrier strip connectors shall be provided for input and output signal wiring. The
unit shall be provided with a front panel power switch with an LED indicator showing Power On
status. The input amplifier shall include a gain control with a ±12 dB range. An LED indicator shall
be supplied to monitor both input and output levels and shall illuminate when either comes within
3 dB of clipping. Dimensions (W x H x D) shall be 19.0" x 3.5" x 12.5" (483 x 88 x 317 mm) with
rack-mount brackets attached, and shall occupy two standard  rack spaces. A smoked plastic
security cover shall be provided.

The 1/3 octave graphic equalizer shall be TOA model E-1231.