Table of Contents
Advertisement
COMMON ANALOGUE GROUNDING ISSUES
Correctly connecting the Intellivox to ground has several
benefits:
1.
Safety – the Protective Earth terminal of
the AC mains connector provides a direct
low impedance path from the metal parts
of the chassis to ground. Always connect
this terminal.
2. Reduction of RF emission – although the Intellivox
electronics are well shielded and external connections
are decoupled to prevent RF emission from the internal
high speed digital circuits, this protection will not work
properly if the chassis is not connected to ground.
3. RF Immunity – RF currents induced in the signal cables
by external RF fields are effectively shorted to chassis-
ground, provided that the cable screen (shield) is of
sufficiently low impedance.
In addition to the mains ground, the Intellivox connectors
have ground pins marked in two different ways. Each
serves a dedicated purpose and care should be taken that
they are not interchanged or connected to each other.
• Pins marked GND are connected internally directly to
the chassis of the Intellivox. There are GND pins on the
audio line input connectors. These GND pins are for
connecting the screen (shield) of the audio cables.
• The RS-485 connector has one pin marked DGND and
is intended as a terminal for the network cable screen
(shield). Since the RS-485 interface is optically isolated
(to prevent ground loops), DGND has no relation to the
chassis ground. DGND should not be connected to any
other ground pin (GND) on the chassis.
24
JBL
Intellivox HP series Installation Manual Rev 1.2
®
SOFTWARE AND FIRMWARE UPDATES
The JBL WinControl application is freely available and can
be downloaded from the download area of our website;
www.jblpro.com. We advise installers, users and engineers
to check our site regularly for updates. Intellivox firmware
and DSP software upgrades will also be made available
through the website.
For further information about how to use WinControl
please refer to the WinControl Help files.
NETWORK CABLES
The type of cable necessary for correct operation of the
RS-485 network is twin twisted pair with each pair
individually shielded. Numerous cables of this type
are readily available and cables broadly meeting the
specifications of the example cable given below are likely
to be suitable.
Example of a preferred cable type:
PARAMETER
Type
Characteristic impedance
Capacitance (core to core)
Capacitance (core to screen) 72.5 pF/m
DC resistance (core)
DC resistance (screen)
VALUE
BELDEN 'Datalene' series
No. 9729 2-pair
100 ohms
41 pF/m
78.7 ohms/km
59.1 ohms/km
201601/IvxHPIM_v1.2
Advertisement
Table of Contents
