Crown Audio IQ-P.I.P.-SLM User Manual

Page 18

Page 18

IQ–P.I.P.–SLM Programmable Input Processor with Load Monitoring for IQ Systems

Reference Manual

commands and data. As implemented in the

IQ–P.I.P.–

SLM, it is a 20 milliamp current loop operating at a
BAUD rate of 38.4 K. The loop must be unbroken.

If the system includes an

IQ–INT II interface, it can ac-

cept eight different Crown Bus loops or zones. Divid-
ing the sound system into different zones, each with its
own Crown Bus loop, can have several advantages.
The following list contrasts those advantages with
those of a single loop.

Multiloop Advantages

• A break in communication in one loop does not

affect other loops.

• Over 250 IQ components of the same type can

be used in a system.

• The same IQ address can be used more than

once (once per loop per model).

Single Loop Advantages (with IQ-INT II interfaces)

• The

IQ System can send and retrieve data faster

in a single loop.

• “Real time” level display of a greater number of

units is possible.

The

IQ–P.I.P.–SLM can be connected to the Crown Bus

with inexpensive twisted-pair wiring (shielded or un-
shielded). If fiber optic wiring is required, contact the
Crown Technical Support Group (see page 4).

Here are some guidelines for twisted-pair wiring:

• Use unshielded twisted-pair wir

Use unshielded twisted-pair wir

Use unshielded twisted-pair wire

e in most

cases, since unshielded wire has lower capaci-
tance and, typically, interference is not a prob-
lem. However, when interference is a problem,
you should use shielded twisted-pair wiring at
least 26 AWG in size. The wire should be of
good quality and should have low capaci-
tance—30 picofarads/foot or less is good. (West
Penn 452 or an equivalent wire works well.) The
shield serves two purposes: First, it helps pre-
vent the IQ data signal from transmitting to
nearby audio wiring. Second, it helps prevent
outside RF from interfering with the data signal.
•

Minimize the total capacitance of each

Crown Bus loop.

own Bus loop.

own Bus loop. The total capacitance should

be less than 30 nanofarads. Allow for approxi-
mately 60 picofarads for each IQ component in
a loop. This accounts for a slight delay which
occurs as data signals pass through a compo-
nent.

• Add an IQ Repeater

Add an IQ Repeater

Add an IQ Repeater for very long loops—
greater than 1,000 feet (305 m)—or when re-

3/16 in

(0.48 cm)

Fig. 4.4 A Removable, Eurostyle Mating Plug

quired by high-capacitance wire. Although we
recommend a repeater for loops longer than
1,000 feet, it is often possible to go 2,000 feet
(610 m) or more. The most significant character-
istic of the wire is its capacitance. Lower capaci-
tance allows longer loops. Unshielded wire
usually has less capacitance.

• Never use the gr

Never use the gr

Never use the ground wir

ound wir

ound wire in a mic snake

e in a mic snake

line.

line. It may sometimes be convenient to run
Crown Bus data signals to and from stage moni-
tor amplifiers along unused wire pairs in a mic
snake. Do not use the ground wire which is nor-
mally connected to pin 1 on an XLR connector
or data noise will be added to the audio lines.
Use only the signal lines which normally con-
nect to pins 2 and 3 of the XLRs.

Note: Because

typical mic cables have high capacitance, the
maximum possible Crown Bus loop distance will
be less.

Outside RF interference is seldom a problem for a
Crown Bus loop—especially if shielded twisted-pair
wire is used. However, there are extreme situations
when fiber optic wiring is recommended. For example,
locating a Crown Bus loop next to an AM radio trans-
mission line may require fiber optic cabling. An ex-
tremely long Crown Bus loop distance may also require
fiber optic cabling.

There are two different types of connectors used for
Crown Bus wiring: DIN connectors and removable
Eurostyle barrier block connectors. The

IQ–P.I.P.–SLM

uses a single 4-pin Eurostyle barrier block connector
that accepts a removable mating plug like the one
shown in Figure 4.4.

For reliable connection, cleanly strip the jacket from the
wire, twist and fold conductor back over the jacket. In-
sert wire into Eurostyle connector and tighten the set
screw.