Asl intercom PS 278TR User Manual

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PRO SERIES

USER MANUAL

FOR THE

PS 278

DUAL CHANNEL MASTER STATION

CONTENTS

1.0 GENERAL DESCRIPTION ...................... 1

2.0 UNPACKING ................................. 1

3.0 MECHANICAL INSTALLATION ................... 1

4.0 MAINS POWER ............................... 2

5.0 FRONT PANEL CONTROLS ..................... 4

6.0 REAR PANEL CONTROLS AND CONNECTORS .... 6

7.0 INTERNAL CONTROLS ........................ 7

8.0 CABLING .................................... 8

9.0 PARTY LINE, TECHNICAL CONCEPT ............. 9

10.0 GUARANTEE ................................. 9

11.0 DESIGN CRITERIA ............................ 9

12.0 TECHNICAL SPECIFICATIONS ................. 10

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1.0 GENERAL DESCRIPTION

The PS 278 is designed to be a master unit in an ASL The unique ASL CALL system provides both a flashing red intercom system and can be used in portable as well as LED and a very distinctive and characteristic sound signal. fixed applications. It incorporates a dual channel intercom Only a slight touch of the CALL button will make the LED line power supply, a dual channel headset station, an flash, whilst holding the button for two seconds will activate audio input and uses only 1U of 19" rack space. the call sound signal. In case the sound signal is

undesirable, all buzzers can be muted with the front panel This makes the PS 278 very versatile and ideal for use in 'all buzzers on/off' button. applications where standard microphone cable is available and ease of setup is of paramount importance. Fully electronic switching increases reliability and allows

for : Each channel has a Volume (listen level) control, a Talk - 'soft' microphone ON switching, latched or momentary and a Call button with LED indicators and a sidetone - remote Mic Mute facility. All microphones of stations trimmer. connected to the PS 278 can be muted by pushing a

single front panel button. The intercom line power supply is fully protected and can drive at least 20 beltpacks or 10 speaker stations, or a An Aux input on the rear panel, allows injecting external combination, operating at full power. The power supply is audio signals of line or mic level. When 'mic level' is completely separated from all other functions and in case selected, +30 V phantom power is available at the Aux of power failure the unit can accept line power from an input connector. external ASL power supply. An Aux signal can be routed to intercom line A and/or B, or

directly to the local headset. Since the power supply provides the line impedance, only one PS 278 should be used on the two channels. For As an option, a XLR-6 headset connector can be fitted, driving more beltpacks/speaker stations on these lines an allowing the user to hear channel A + AUX program signal additional power supply booster (PS 285) is needed. on the left headset can and channel B + AUX program

signal on the right headset can. By changing the position Special attention has been paid to the intelligibility of of internally mounted jumpers, it's also possible to hear speech. By applying low noise/high speed circuitry, channel A + B on the left can and the AUX program signal a speech presence filter and a specially designed high on the right can. power headphone amplifier, communication is very comfortable even in environments with a high background noise level.

2.0 UNPACKING

The shipping carton contains the parts listed below. ASL has taken great care to ensure that this product

* The PS 278 reaches you in flawless condition. * Power cable After unpacking the unit please inspect for any physical * Spare fuses damage to the unit, and retain the shipping carton and * User manual relevant packing materials for use should the unit need

If any are missing contact your dealer. returning. With the PS 278 will be a small packet of spare fuses. If any damage has occured, please notify your dealer

Please keep them in a safe place. immediately so that a written claim can be initiated. Please There is also one spare fuse included in the mains inlet. also refer to the guarantee section of this manual.

3.0 MECHANICAL INSTALLATION

A vertical rack space of 1U (1.75", 44mm) is required for required. the PS 278. It is not necessary to provide rear support by extra bracing or shelving. The power supply regulator is mounted on the rear of the

unit, and after a period of time it will feel hot to the touch. Adequate ventilation must be provided by allowing This is quite normal, and should be no cause for alarm. sufficient space around the sides and rear of the unit to ensure free circulation of air. Forced cooling is not

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4.0 MAINS POWER

The PS 278 may be connected to the mains power outlet to which other audio equipment is connected. The outlet The wires in this mains lead are colour coded in should have a clean safety earth. Avoid using mains accordance with the following code: power outlets which also power dimmer controlled lighting equipment. green and yellow Earth / safety ground

Before connecting the unit to its AC power source, check if Neutral the mains voltage setting is set in accordance with your brown local mains voltage. The voltage setting is indicated by a Live label on the rear panel.

If a change is necessary, the internal mains transformer correspond with the coloured markings identifying the wiring will need to be reconnected as shown in section 4.3 terminals in your plug, proceed as follows: Mains Power settings. Remember that the AC mains fuse will need to be - The wire which is coloured green-and-yellow must be changed for one of the correct rating as indicated. connected to the terminal in the plug which is marked

The power cord supplied with this unit carries the following coloured green. information label: - The wire which is coloured blue must be connected to

WARNING

This appliance must be earthed

IMPORTANT

blue

As the colours of the wires in the mains lead may not

with the letter "E", or by the earth symbol which is or

the terminal which is marked with the letter "N" or coloured black.

- The wire which is coloured brown must be connected to the terminal which is marked with the letter "L" or coloured red.

Those units that are supplied to the North American market will have an integral moulded 3 pin connector which is provided to satisfy required local standards.

4.1 SAFETY EARTHING

The green-and-yellow wire of the mains cord must always be connected to the electrical installation safety earth or ground. It is essential for personal safety as well for proper operation of the PS 278 and the other connected stations. This wire is internally connected to all exposed metal surfaces and any rack framework into which this unit might be mounted is assumed to be connected to the same grounding circuit.

The PS 278 employs professionally designed audio input and output circuits which do not require the disconnection of any safety earth for the avoidance of hum loops.

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4.2 POWERING UP

Powering up procedure:

- Make sure that the red power switch on the left side of the front panel is OFF.

- Connect the power cord to the rear of the station.

- Plug the other end of the power cord into a PROPERLY GROUNDED outlet.

- Turn on the power with the red button. The red overload LED will light up for about 3 seconds, then extinguish and then the green power LED will go on, indicating that the station is active.

4.3 MAINS POWER SETTING

Voltage settings

See also section 4.0 Mains Power

Setting for 115 V AC

1. Red + Green

2. Empty

3. White + Yellow

Setting for 230 V AC

1. Red

2. White + Green

3. Yellow

Mains Fuse

100 - 120V T 630 mA 220 - 240V T 315 mA

(Top View)

Voltage:

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5.0 FRONT PANEL CONTROLS

1 POWER ON/OFF switch 7 ALL BUZZERS ON/OFF button

Mains power push button for switching ON and OFF With this button all buzzers of the connected stations the internal power supply. can be muted.

2 OVERLOAD LED 8 AUX VOLUME control knob

This LED illuminates if the internal power supply has This knob adjusts the level of the aux input signal shut off line power due to overload. before it is sent either to the intercom line(s) or to the If the internal power supply is overloaded (too many headset (see also section 5.8). user stations are connected, or short-circuit in the interconnecting cables, or thermal overload), it activates a circuit-breaker which immediately shuts off These three switches route the aux input signal to line power. This circuit breaker resets automatically either: 3 seconds after the overload situation is terminated, 1) Intercom channel A and/or Intercom channel B restoring line power automatically. 2) Directly to the headset During short-circuit, the LED will flash every 3 If the aux is routed to the headset the aux is for local seconds. During thermal overload it will remain on monitoring only, and can not be routed to the intercom continuously. channels. The LED will also come on for a few seconds every time you switch on the mains power.

3 POWER LED

This LED illuminates if line power is supplied by the internal power supply.

4 BUZZER

This buzzer indicates an incoming our outgoing call. It is activated by pressing a CALL button of the PS 278 or a CALL button of any other station on channel A or B for longer than two seconds and the buzzers are not muted (see 5.7). You can adjust its volume with the buzzer volume control.

9 A/B/HEADSET routing switches

5 BUZZER VOLUME trimmer

This trimmer adjusts the volume of the buzzer.

6 ALL MIC'S ON/OFF button

With this pushbutton all microphones of the connected stations can be muted.

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5.0 FRONT PANEL CONTROLS

10 VOLUME control knobs 13 CALL A & B buttons

These knobs adjusts the listen level for the headset. These push buttons activate the CALL system. Each channel can be adjusted separately. A momentary push will send a CALL signal to all

stations connected to that intercom channel and the

11 SIDETONE trimmers

These trimmers adjust the level of your own voice as Press and hold the buttons for 2 seconds will activate you hear it in your headset. the call buzzer, if not muted. Adjustment procedure : After the CALL button is released the LEDS will

- set the trimmer in start position: fully clockwise. continue to flash for a further 2 seconds.

- switch off the microphone of all connected

(speaker!) stations.

- switch on the microphone of the required channel. A XLR-4 type connector for the connection of the local

- turn up the volume of the required channel. headset. This must have a can impedance of 200

- speak into the headset microphone. ohms (or greater), or each 400 ohms minimum when in

- adjust the listen level by turning the sidetone parallel. The mic may be of the dynamic or electret

trimmer. type. The operating area is between fully clockwise and minimum level. Adjusting the sidetone does not affect Pin assignments: the level of your voice as it is heard by other stations. 1. shield mic. (GND)

12 TALK buttons

These buttons allow you to talk to each channel 4. phones separately or simultaneously. The large green LED indicates if the talk function is The wiring is such that both headset cans are activated. connected in parallel and receive the same signal. The

Latched switching:

When a TALK button is momentarily pressed, the As an option, a XLR-6 type connector can be fitted to microphone will be switched on for the chosen channel give a binaural headset configuration where a different and is electronically latched. When pressed again, the signal will appear on each can. In this mode the microphone will be switched off. internal headphone amplifiers are not bridged.

Momentary switching:

When a TALK button is pressed and held, the microphone will be switched on, and when released, will be switched off.

CALL LEDS will start flashing.

14 HEADSET connector

2. mic. +

3. phones +

two headphone amplifiers run in a bridged mode.

See section 7.1 Internal Jumpers and Controls.

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6.0 REAR PANEL CONTROLS & CONNECTORS

15 A & B LINE connectors 18 MAINS INLET

These XLR-3 type connectors are for connecting the IEC Mains connector. For correct wiring and operation remote-stations, via standard microphone cable. refer to section 4.0. There are two connectors for channel A and two connectors for channel B.

WARNING

Pin assignments :

1. 0 V / ground shield

2. +30 V power wire

3. audio wire

Before you plug in the mains voltage, check if:



The fuse is correct



The voltage is correct

16 AUX INPUT connector

This XLR-3 type aux input is electronically balanced and accepts audio levels between -18dBu to +22dBu on line level, and -38dBu to +2dBu on mic level.

Pin assignments :

1. 0 V / ground

2. Signal +

3. Signal -

When mic level is selected, a +30Vdc phantom power is supplied to pins 2 and 3.

17 FUSE

This fuse protects the PS 278 against severe internal damage, in case of malfunction in the power section. To remove the fuse the mains cord must be removed. It is most important to place the correct fuse in the holder : mains voltage fuse 220 - 240 VAC T 315 mA 100 - 120 VAC T 630 mA Spare fuses will be found in the small packet supplied with the unit.

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7.0 INTERNAL CONTROLS

MIC GAIN

The mic gain can be adjusted internally.

- Open the PS 278 with the two top screws at the

frontpanel and the two screws top side

The trimmer is located at the right front of the unit.

To increase mic gain turn clockwise.

To decrease mic gain turn counterclockwise. See section 7.1 for the location of the mic gain trimmer.

7.1 INTERNAL JUMPER SETTINGS AND CONTROLS

Binaural Jumper settings

See also section 5.0 -14 HEADSET connector The binaural configuration is set by internal jumpers J3,

as follows: Jumpers in position A

Left can channel A and B. Right can AUX-signal.

Jumpers in position B Left can channel A and AUX-signal. Right can channel B and AUX-signal.

Internal mic gain

See also section 7.0 - Internal Controls The mic gain trimmer is labeled:

P2 for the mic gain setting.

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8.0 CABLING

For the PRO Series Intercom system the interconnecting cables are of the shielded two-conductor microphone cable type and the intercom line connectors are of the XLR-3 type. Audio and Call signals are on XLR pin 3, DC power is on XLR pin 2. XLR pin 1 is connected to the shield of the cable which functions as the common return for audio and power.

Since the audio signal is transferred in an way, certain rules have to be obeyed when installing the cables of an intercom network. This is to avoid earth loops and to minimize power loss and the possible effect of electromagnetic fields.

These rules are:

Use high quality (multipair) cable.



For interconnecting user stations, power supplies and When two (multi channel) units in a network are accessories in an ASL Intercom network, use high connected by more than one cable, make sure that quality shielded two-conductor (minimum 2x 0.30 mm2) these cables are parallel to each other over the whole microphone cable only. distance between those units. When using multipair In case of a multi channel intercom network, use high cable, parallelism is ensured in the best possible way. quality microphone 'multipair' cable only, each pair consisting of two conductors (minimum 2x 0.15 mm2) with separate shield. Multipair cable should also have Always avoid that cables are making a loop. So-called an overall shield. 'ring intercom' should not physically be cabled as a

Use flexible cables.

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Use flexible single and multipair microphone cable power supply position) as the centre of the star. instead of cable with solid cores, especially when the cable is subjected to bending during operation or installation. Keep intercom cables away from high energy cables,

Separate cable screen to XLR pin 1.



The screen of each separate microphone cable and/or Intercom cables should cross high energy cables at an the screen of each single pair in a multipair cable, angle of 90( only. should be connected to pin 1 of each XLR-3 connector. Intercom cables should never be in the same trunking Do not connect this cable screen to the metal housing as energy cables. of the connector or to metal wall boxes (outlets). See page 13 for Earthing Concept.

Cable trunks, connection boxes and overall



multipair cable screen to clean earth.

Metal cable trunks, metal connection boxes and overall user stations are placed. multipair cable screen should be interconnected and, at one point (the 'central earthing point') in the intercom network only, be connected to a clean safety earth. See page 13 for Earthing Concept. The ASL power supply may be connected to the mains

Keep metal connection boxes and cable trunks



isolated from other metal parts.

Metal housings for intercom cables and connectors should be mounted in such a way that they are isolated In case of more complex installations, don't hesitate to from other metal cable and connector housings and contact us. Please send us a block diagram of the from any other metal construction parts. planned network with a list of all user stations and their

See Party Line, Technical Concept

unbalanced

Keep cables parallel as much as possible

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Avoid closed loops.

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ring. All cable routes should have a 'star' configuration, with the central earthing point (usually close to the

Keep cables away from electromagnetic sources.

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e.g. 110/220/380V mains power or dimmer controlled feeds for spotlights.

Place power supplies in a central position.

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In order to avoid unacceptable power losses, place the power supplies as close as possible to where most power consumption occurs or, in other words, most

Connect ASL power supply to a 'clean' mains



outlet.

power outlet to which other audio equipment is connected. Avoid using mains outlets which also power dimmer controlled lighting systems.

positions, and we are happy to advise you on cabling lay-out.

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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

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 interconnecting cables.

10.0 GUARANTEE

This unit is warranted by ASL Intercom to the original enduser 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.

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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12.0 TECHNICAL SPECIFICATIONS PS 278

POWER SUPPLY

mains voltage range 115 V units: 100 - 125 V 60Hz AC

230 V units: 210 - 250 V 50Hz AC DC output voltage +30 V +/-5% DC ripple and noise < 11 mV rms max. output current 1.7 A continuous / 3 A peak circuit-breaker delay time 0.2 sec. automatic reset time 3.0 sec.

AUX INPUT

input impedance 30 Kohms (balanced line level)

4.6 Kohms (balanced mic level)

nominal input level -18 dBu to +6 dBu (line level)

-38 dBu to -14 dBu (mic level)

max. input level +22 dBu (line level)

+2 dBu (mic level)

phantom power +30 V DC (mic level selected)

MIC. PREAMP

mic. impedance 200 ohms gain 40 dB - 70 dB (adjustable internally) presence filter +6 dB at 5 kHz frequency response 200 Hz - 13 kHz (-6 dB) V electret mic + 9 V DC

HEADPHONES DRIVER AMP

max. load 200 ohms max. output level normal 14 V rms (200 ohms)

binaural 8 V rms (400 ohms)

max. output power normal 0.5 W rms (each can)

binaural 0.16 W rms (each can)

SIDETONE

rejection 0 - 30 dB adjustable

BUZZER

max. SPL 100 dBA

DIMENSIONS AND WEIGHT

width 19" (483 mm) height 1U (44.5 mm) depth 150 mm weight 2.75 Kg

GENERAL SYSTEM SPECIFICATIONS

intercom line impedance 350 ohms (1kHz)

2.2 Kohms (DC)

intercom line audio level nom. -18 dBu

max. +4 dBu dynamic range 80 dB call send signal 2.8 mA call receive signal threshold +2.4 V DC supply voltage +30 V DC (12 V to 32 V) mic mute power interrupt time 0.1 sec

Note: 0 dBu = 775 mV into open circuit. ASL reserves the right to alter specifications without further

notice.

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