User Manual PS 278 / Issue 2 © 1996 ASL Intercom, Utrecht, Holland.
9
9.0 PARTY LINE, TECHNICAL CONCEPT 11.0 DESIGN CRITERIA
ASL's PRO Series offers a complete two way ('full duplex')
communications system. ASL Pro Series equipment is designed for use as a wired
Users of the system are connected via a 'party line'. communications system in theatres, in Radio/TV
Master stations (with built-in power supply), beltpacks, production facilities, in factories, and in utilities complexes
speaker stations and power supplies are interconnected such as airports, railway stations and coach terminals.
via standard microphone cable. One wire is used as an
audio line, one as a power line and the screen of the cable ASL equipment can be used outdoors in normal weather
functions as earth/return. conditions. In conditions with excessive cold (<-10
(
C),
Current drive is used for signal transfer. Each station not perform properly.
utilises a current amplifier to amplify the microphone signal
and place it on the common audio line where, due to the ASL equipment is not designed to be used under water, or
constant line impedance (situated in the power supply in situations where explosion safe equipment is specified
between XLR pin 3 and 1), a signal voltage is developed by authorities.
which can be further amplified and sent to headphones or
loudspeakers.
This principle has three advantages: ASL Pro Series equipment does not generate high
- the use of a single audio line allows several stations to frequency (HF) signals. An ASL power supply can
talk and listen simultaneously. generate a weak magnetic field caused by the power
- due to the high bridging impedance offered by each transformer. To avoid possible negative effects, keep ASL
station, the number of stations 'on line' has no power supplies at a safe distance from equipment which is
influence on the level of the communications signal. very sensitive to magnetic fields.
- power and audio to the intercom stations use the same
cable.
The Call signal is also sent as a current on the audio line. ASL Pro Series is designed on the base of low impedance
It develops a DC potential over the line impedance which signal transport. User stations and power supplies are to
will be sensed by each station and interpreted as a Call be connected via low capacity cabling with an overall
signal. screen (see also Cabling section). Therefore, HF signals
10.0 GUARANTEE
This unit is warranted by ASL Intercom to the original end-
user purchaser against defects in workmanship and
materials in it's manufacture for a period of one year from
the date of shipment to the end-user.
Faults arising from misuse, unauthorised modifications or
accidents are not covered by this warranty. If the unit is
faulty, it should be sent in it's original packing to the
supplier or your local ASL dealer, with shipping prepaid. A
note must be included stating the faults found and a copy
of the original suppliers invoice.
Applications / Environment of use
heat (>50
(
C) or humidity (>85%), ASL equipment might
Emission
Immunity
are adequately rejected to maintain an intelligible
communication, unless strong electro-magnetic fields
(exceeding 3V/m) are in the direct vicinity of the intercon-
necting cables.
ASL 19" rackmount units are housed in a 1 mm steel
enclosure (closed construction), which offers, by nature,
the highest possible rejection of electro-magnetic fields.
ASL speaker stations (PS 130/230/430) are housed in an
enclosure made of 1 mm steel with ABS side panels,
which offers adequate rejection of electro-magnetic fields.
ASL beltpacks are housed in an ABS enclosure and are
slightly more sensitive to electro-magnetic fields. Negative
effects in the performance of beltpacks can be avoided
when keeping them on a safe distance from equipment
which might radiate strong electro-magnetic fields, such as
transmitter antennas and dimmers.
THIS PRODUCT WAS DESIGNED, DEVELOPED AND
MANUFACTURED BY :
AMPCO SOUND LAB BV
MAARSSEN (UTRECHT) HOLLAND
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