Virtual Systems 1441Crossovers, system equalizers, and delays are some of the
more common examples of this class of device.
Until the introduction of the inexpensive graphically
oriented personal computer, there was no practical way
to avoid this cost, or to provide other than physical limi-
tation of access to controls. Once graphical computers
became commonplace and inexpensive, we saw the
introduction of a new class of digitally controlled
analog devices. These devices had greatly reduced
numbers of physical controls, and in some cases had no
physical controls. Instead the devices were adjusted by
connecting them to a personal computer and running a
control program on the computer. Once the “controls”
were set using the program, the computer could be
disconnected and the device would retain the settings
indefinitely.
Since there were no or a limited subset of actual
physical controls, there was no need for physical access
restriction devices. Without both a computer and the
appropriate control program, there was no way for the
user to adjust the controls.
Presets, which could be recalled either from the front
panel or remotely, now became possible. Different
system configurations, which required multiple changes
to controls, now became as simple as pressing a single
button.
Computer control also allowed many more controls
to be provided on a physically small product than would
otherwise be practical. For example, a -octave equal-
izer might have 27 bands, plus a number of presets, and
yet could be packaged in a small box.
Remote control of the device allows the control point
to be distant from the audio device itself. This opened
the possibility of reducing the amount of audio cabling
in a system and replacing it with inexpensive data
cabling to the operator’s control point. The data cabling
is much more resistant to outside interference than
audio cabling.
In the initial versions of such control systems, a
different control program and physical connection from
the computer to the audio device was required for each
device that was to be so controlled. This was fine in
smaller systems, but in larger installations where there
might be many such digitally controllable devices, it
quickly became cumbersome.
To address this limitation, Crown developed what
they called the IQ system. It used a single control
program together with a control network that connected
many digitally controllable devices. Thus it provided a
single virtual control surface on a computer screen,
which allowed the adjustment and monitoring of
multiple individual audio devices.
38.2.2 Digitally Controlled Digital Audio DevicesEarly digital audio devices had physical controls that
mimicked the controls of analog devices. As with digi-
tally controlled analog devices, the advantages of remote
control programs quickly became apparent, particularly
for those devices with many controls.
Digital audio devices already were internally digi-
tally controlled, so providing for remote control was an
easy and relatively inexpensive step. Some such devices
provided physical controls that communicated with the
signal processor. Others provided only control programs
that would run on a personal computer and connect via
a data connection back to the device controlled.
As with the digitally controlled analog devices, most
such control schemes required an individual data line
from the control computer to each device controlled.
Several manufacturers including TOA and BSS devel-
oped techniques to allow many of their devices to be
controlled by a single data line. These schemes were
limited to products of a single manufacturer. Work went
on for many years under the auspices of the Audio
Engineering Society to try to develop a universally
applicable common control scheme, but the require-
ments were so diverse that a universal standard has yet
to be achieved.
This was one of the factors leading to the rise of
universal control systems from companies such as
Crestron and AMX that have the ability to control and
automate remote controllable equipment using any
control protocol. For the first time such control systems
allow the user to have a single control surface that oper-
ates all these systems with their diverse control proto-
cols. These control systems control audio, video,
lighting, security, and mechanical systems, allowing a
degree of total system integration never before achieved.
Despite the success of these universal control
systems, often the user just needs to control all his or
her audio system components from a single interface.
This has been a driving force behind the continued
efforts to develop a common control protocol, or some
other easy way to bring all these controls together for
the user. Besides the work that the AES has done toward
developing such a common protocol, control and moni-
toring protocols developed for other industries have
been adapted for use with audio systems. Among these
protocols are Simple Network Management Protocol, or
SNMP, and Echelon LonWorks.
The desire for unified systems with reduced control
interfaces has also been one reason for the popularity of
integrated devices that combine the functions of many
formerly discrete devices in a single unified product.(^1) » 3