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The Models 3340 and 3342, illustrated in Figure 1, are variable, electronic Filters with digitally tuned cutoff frequencies over the range from 0. 001 Hz to 99. 9 kHz. The passband gain is unity (0 db) or 10 (20 db), with attenuation rates of 48 db per octave (Model 3340) or 96 db per octave (Model 3342} outside the passband. Maximum attenuation is greater than 80 db, and the output hum and noise is less than 500 microvolts. The Model 3340 can function as either a High-Pass or Low-Pass Filter. In the High-Pass mode of operation the maximum input signal isi plus or minus 7 volts peak in the 0 db gain position, plus or minus :0. 7 volts peak in the 20 db gain position, and the upper 3 db point occurs at approximately 1 MHz. In the Low-Pass mode the Filter is direct-coupled, and the combined ac plus dc input signal should not exceed 7 volts peak in the 0 db gain position and 0, 7 volts peak in the 20 db gain position. The models 3341 and 3343 are identical to the 3340 and 3342, respectfully, except for the elimination of the lowest band (. 001}. The Model 3342 consists of two of the Model 3340 mounted in a single cabinet isolated from each other with independent power supplies, and input and output connectors. ;When these two Filter channels are switched to the same mode of operation and connected in series with both channels set to the same cutoff frequency, the Model 3342 will function as a High-Pass or Low-Pass Filter with an attenuation rate of 96 db per octave. If the two channels are connected in series, and one channel is operated in the Low- Pass mode and the other channel in the High-Pass mode, the Model 3342 will function as a Band-Pass Filter with an attenuation rate of 48 db per octave outside the pass-band. When the two channels are connected in parallel, as described in Section 2. 3. 2. 3, the Model 3342 will function as either a Band-Reject Filter with cutoff frequency limits from 0. 001 Hz to 99. 9 kHz or provide a null at any frequency between 0. 003 Hz and 30 kHz. The Filter has a maximally flat (Butterworth} characteristic when the FUNCTION switch(s} is in the Low-Pass MAX FLAT position. For pulse-type wave-forms this switch should be in the Low-Pass RC position, optimum for transient-free filtering. The term (RC} as used in this manual may be misleading. It is not an 8 pole RC Filter. A certain amount of feedback still remains in 3 of the two-pole sections.