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PLM Series Operation Manual rev 1.1.3
11. Appendix
11.5 Glossary of Terms, Acronyms and Abbreviations
The explanations given in table 11.6 are based on the specific use of each term in this manual. The defini-
tions are not intended to be exhaustive. Many of the terms have wider meanings!
Term
Description
10/100Base-T
10Base-T and 100Base-T are IT industry-speak for two different standards of Ethernet network. In broad terms, the older 10Base-T
operates at 10Mbps but has now been largely supplanted by the 100Mbps 100Base-T.
Access Point
See Wireless Access Point.
Auto-sensing
The Ethernet ports on the PLM automatically determine the base speed of the network they are connected to (10Base-T or 100Base-T) and
configure themselves appropriately. This is termed auto-sensing.
Auto-uplink
The Ethernet ports on the PLM are able to operate with either straight or crossed network cables. This ability to connect correctly with
either type is termed auto-uplinking.
Auxiliary output
Some of the configurations possible in the Dolby Lake processing system Modules result in a single audio processing channel being created
in addition to a crossover. This is termed an Auxiliary output.
Backbone
Large Ethernet networks are often implemented with a very high speed “trunk” part of the network topology feeding main switches, which
in turn support smaller, lower-speed local networks. The term backbone is used to describe such a trunk.
Bandwidth
The bandwidth of a signal channel or interconnection is the range of frequencies it is able to handle. The term can be applied to both audio
channels and Ethernet networks.
Cat-5e/Cat-6, etc.
Designations of industry-standard cables suitable for Ethernet networks using four twisted pairs of conductors. Often referred to as UTP
cable (Unscreened Twisted Pair). Cat-5 has generally been replaced by Cat-5e (e = ‘enhanced’). Either Cat-5e or Cat-6 cable are suitable
for networking the PLM.
Chain
An Ethernet network comprising several PLMs (or other devices) interconnected using the Secondary connectors to daisy-chain the units
together is an example of a network with a chain topology.
Clock
Digital audio is produced by sampling analog audio at a known, fixed rate, controlled by some form of master clock. Problems can occur
when interconnecting two pieces of digital audio equipment if their internal master clocks are not synchronized. Various techniques may
be employed to ensure that this is the case.
CPL
Short for Current Peak Limiter, a Lab.gruppen protection technique which ensures that the amplifier’s output transistors can never attempt
to deliver more than their rated current.
Crossed network
cable
An Ethernet cable in which four of the eight conductors (pins 1, 2, 5 & 6) are not wired pin-to-pin. Such a cable is required in conventional IT
networks to connect two PCs together without using a hub or switch. The auto-uplink feature of the PLM’s Ethernet ports allows crossed
cables to be used if wished. See also Straight network cable.
Dante
A new-generation audio data protocol developed by Audinate
®
Pty Ltd, allowing multichannel high-resolution digital audio plus control data
to be transmitted via standard IT-industry networks using TCP/IP data packeting. The Dolby Lake processing system integrated within the
PLM includes a Dante interface, which can provide the audio inputs to the PLM.
dBu
dBu’s are usually used instead of voltages to describe signal levels in audio systems. A signal level of 0 dBu may be taken as 0,775 Vrms.
Delay
It is possible to delay the audio signal in each of the PLM’s inputs and/or output channels to time-align loudspeaker arrays.
Digital gain offset
Digital gain offset is effectively a ‘fine’ gain adjustment performed in the digital domain, which can be applied to digital input signals to
optimise the signal to the PLM’s gain structure.
Distribution amplifier
A distribution amplifier (usually abbreviated to DA) is an audio buffer stage – usually with zero gain – with one input and several outputs.
Mono, stereo and AES/EBU digital versions can be obtained. Use of a DA to feed a signal to several destinations ensures correct impedance
matching and isolation between source and destinations.
Dolby Lake Processor
A stand-alone loudspeaker management system manufactured by Dolby using Lake technology. The Lake Processing system integrated in
the PLM is a slightly scaled-version of the Dolby Lake Processor.
Dual-network
topology
A network topology consisting of two (usually) identical networks, one connecting to the Primary Ethernet ports and the other to the
Secondary ports. Although more complex to implement, the advantage of using a dual-network system is one of greatly improved reliability
as one complete network remains operational if the other should fail.
Electronic balancing
See Balancing. In the analog domain, balanced inputs and outputs may be provided on audio equipment either by the use of transformers
(traditional, very good, but heavy and expensive) or via electronic balancing circuits (nearly as good, without full electrical isolation, but a
great deal cheaper).
Event log
The details of any fault or warning conditions which arise in the PLM during operation are recorded in a data file created by the Lake
Controller software called the Event Log.
Fault
A Fault in the PLM occurs when one of the PLM’s operating parameters exceeds pre-determined safety levels, or when a condition is
detected that otherwise seriously affects the PLM’s performance. Some fault conditions may result in one or all of the PLM channels
being muted.
Fingerprint
The Lake Controller comes includes LoadLibrary consisting of data describing the electrical characteristics of commonly-used loudspeakers.
The file for each speaker type is termed its Fingerprint.
Finite impulse
response (filter)
An alternative design of crossover filter realisable in the digital domain, providing linear phase characteristics. FIR filtering is provided in the
Lake Processing within the PLM.
