Crown Audio IQ-PIP-USP2_CN - Manual (Page 46)

IQ-PIP-USP2/CN
Page 46 IQ-PIP-USP2/CN Reference Manual
10.3 IQ Bus Wiring
The IQ-PIP-USP2/CN must be con-
nected to a IQ Bus loop having an
IQ2-compatible IQ interface in or-
der for the IQ System to control or
monitor it. The IQ Bus is a serial
communication loop designed to
transmit IQ commands and data. As
implemented in the IQ-PIP-USP2/
CN, it is a 20 milliamp current loop
operating at a BAUD rate of 38.4 K.
The loop must be unbroken to func-
tion properly.
If the system includes an IQ–INT II
interface, it can accept eight differ-
ent IQ Bus loops or zones. Dividing
the sound system into different
zones, each with its own IQ 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-PIP-USP2/CN can be con-
nected to the IQ Bus with inexpen-
sive twisted-pair wiring (shielded or
unshielded). If fiber optic wiring is
required contact the Crown Techni-
cal Support Group (see page 2).
Here are some guidelines for twisted-
pair wiring:
• Use shielded twisted-pair wire
at least 26 AWG in size when
interference is a problem. The
wire should be of good quality
and should have low
capacitance—30 picofarads/
foot or less is good. (West Penn
452 or an equivalent wire works
well.) The shield serves two
purposes: First, it helps prevent
the IQ data signal from
transmitting to nearby audio
wiring. Second, it helps prevent
outside RF from interfering with
the data signal. However, in most
cases interference is not a
problem and, since unshielded
wire has lower capacitance, it is
a better choice.
• Minimize the total capacitance
of each IQ Bus loop.
The total
capacitance should be less than
30 nanofarads. Allow for
approximately 60 picofarads for
each IQ component in a loop.
This accounts for a slight delay
which occurs as data signals
pass through a component.
• Add an IQ Repeater for very
long loops—greater than 1,000
feet (305 m)—or when required
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 characteristic
of the wire is its capacitance.