Hammond A Manual page 40

Two expression pedals are provided for the Model E Console. Both are
equipped with adjustable clamps to regulate the tension and the distance
through which they move. Adjustable pedal indicators, operated by wires
from the rheostat box, are located at the extreme right side of the console
above the Swell manual.
FIGURE 6
The tremulant or tremolo is a periodic variation in intensity of all tones
without change in pitch. It is produced by a variable resistance driven by
the motor of the main tone generator, and is controlled by a variable resistor
in shunt. When the tremulant control is turned as far as possible to the left,
the tremulant is entirely off. As it is turned to the right (clockwise) the degree
of tremolo gradually increases until it reaches a maximum at the extreme right
position. The white dot marker on the knob indicates at a glance the degree of
tremolo present. Two tremulant controls are used on the Model E console, one
for each manual. These are controlled by separate levers located on the console.
The tremulant is not incorporated in models having
FIGURE 7
scanner, mounted on the main tone generator, picks up successive signals from
various line sections. These signals represent various amounts of phase shift, and
the combination of signals produces a continuous frequency variation.
ECHO SWITCH
Located above the starting and running switches
on some consoles is the echo switch (Fig. 6).
With this switch it is possible to use two tone
cabinets and have either cabinet or both speak,
depending on the position of the switch. Generally
one tone cabinet is placed rather distant from
the console and is called the echo organ. This
feature can be added to a Hammond Organ by
installation of an Echo switch kit.
TREMULANT
VIBRATO
The vibrato effect is created by a periodic
raising and lowering of pitch, and thus is fundamentally
different from a tremolo, or loudness
variation. It is comparable to the effect
produced when a violinist moves his finger
back and forth on a string while playing,
varying the frequency while maintaining
constant volume.
The vibrato mechanism includes an electrical time delay line,
which shifts the phase of all tones fed into it. A rotating
vibrato.
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