Theatre Design & Technology - Winter 1979 - 21

mat would support 128 channels, it was felt that a conventional sixteen-channel, two-scene preset console would be
sufficient for the user tests. This console placed control information on sixteen of the 128 available channels; the remaining 112 channels were left blank.
A question arises at this point as to how the control console
output should be interfaced to the digital, multiplexed format
required by the distributed system. One straightforward approach is to take the 0-10 V analog output presently available
on many consoles. As shown in Figure 6, these outputs are
routed via a multiplexer to an AID converter and then to the
format generator. In fact, this is the method employed in the
sixteen-channel prototype console. In general, for large numbers of channels, this method becomes cumbersome.
An alternate approach is to take advantage of the fact that
in virtually all large systems the data is stored digitally within a
computer memory. In these cases, it would be possible to
eliminate both the 01 A conversion which produces a 0-10 V
signal and the subsequent reconversion to digital form by taking the data directly from the computer memory. An interface
based on this approach is shown in Figure 7.
It is important to note that in order to operate the distributed
dimming system from either a small analog console or a larger
digital one, it is only necessary to change the interface unit;
the remainder of the distributed system-transmission data
format and remote dimmers-remains the same.

FIGURE 7 Block diagram showing a method for interfacing the LightLink system to a control console with digital outputs.

DIgital
Dimmer

'.'ulllplexer

Control
Board

Dimmer

Address
Generator

INTERFACE UNIT

FIGURE 8 In tests of the Light-Link system in an "experimental"
theatre, a single, omnidirectional IR emitter was used to transmit the
control information.

Data In

Temporary

Data
Buffer

f-------. Lon -term
Data Buffer

Address
Detector

-------

---

Address
SWllches

<>0

To date, tests of the system have been conducted in
theatres of two general types-proscenium arch and arena.
Both hardwire and IR modes have been tested.
The use of the hardwire mode in either theatre configuration is relatively straightforward. The dimmers are placed
around the theatre as required and connected to a source of
prime power. Instruments are connected to the dimmer out-

Error
Detector

Data
Ou'

Theatre Trials

Data
Formaller

"'"

""'"

D
f· ..-

Triac
Firing
Generator

t
Triac
&
line Filter

Load

FIGURE 5 Block diagram of the evaluation prototype.

FIGURE 6 Block diagram indicating a method of interfacing the LightLink system to a control console with analog outputs.

--_ ~
;"'"
:;
O'l"rr···

.....

','...I',

n.n'

**. f

,
.
'
8",
g~:~
~[I8-

~
=
h.l

:r.· s

'-"
g.

,'_r'"

F ........ ··**

I
.

FIGURE 9 Tests of the Light-Link system in a proscenium theatre, for
shows needing full masking, required several IR emitters.

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