ARP 2600 - Control Signals: Triggers and Gates; Keyboard Controller Signal Outputs

16
2.212
It is important to
remember that VOLTAGE CONTROL
is
an
extension
of manual control;
in
theory
anything you
can do
with a
voltage you should
be able
to
do
with
a
knob, manually.
IN FACT,
A-
your
hands cannot move fast
enough,
or accurately
enough,
to
come
within
miles of
what
a
voltage
signal
can
do with a
voltage-controlled
des ice.
2.22
Continuously
variable
characteristics such as
the
frequency
of
an
oscillator, the
cutoff
frequency
of a
filter,
or
the gain
of an
amplifier, may be
controlled
by continuously
variable
voltages.
2.23
Other
functions that
may be
controlled
by
electrical
signals are
START functions
and
ON-OFF
functions. Signals
used for
these pur-
poses
are caiied TRIGGERS
and GATES
respectively.
2.231
An
electronically
TRIGGERED
device will
begin
to operate
when a voltage
at
the
proper
input goes
from zero to some positive
voltage and
immediately comes
back
to
zero. On
a
graph
such a
TRIGGER SIGNAL
might
look like
this
2.232
An electronically
GATED device
will begin to operate when
a
voltage
at the proper input
goes from zero
to some
positive
value
AND WILL
CONTINUE
to operate
ONLY
AS
LONG AS the voltage
sta\ s at
or above
that
value.
Thus
a
GATE
SIGNAL
might
look like
this
2.24 A
keyboard
controller
for
a
synthesizer usually works
by some
combination of CONTROL
VOLTAGES to
signal which key
is
pressed
down, GATES to signal
the length
of time a
key
is
down,
and
TRIGGERS to signal
the
exact instant at
which a
key
is
pressed down.
2.25 USING A
SIGNAL
TO
CONTROL
something
in
this
fashion
DOES
NOT MAKE A
DIFFERENCE
to
the SIGNAL.
A
voltage
is
a
voltage is a voltage; there are
control voltages only
where
there is
equipment designed to
be
voltage
controlled.
Calling
a
signal
a
control
signal is
only
saying
what,
in some particular
case, its FUNCTION
is;
namely, that it is
being
fed
to the control
input
of a
voltage-control-
lable device.
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