Clear-Com MS-232 User Manual

Clear-Com MS-232 Two-Channel Main Station

INTRODUCTION

Congratulations on choosing this Clear-Com product. Clear-Com was established in 1968 and remains
the market leader in providing intercom for entertainment, educational, broadcast and industrial appli­cations. The ruggedness and high build-quality of Clear-Com products is the industry standard. In fact,
many of our original beltpacks and main stations are still in daily use around the world.

The MS-232 Two-Channel Main Station is a powerful, yet user friendly unit that can serve as the heart
of a Clear-Com system. We recommend that you read through this manual completely to better under­stand the functions of the MS-232. If you encounter a situation or have a question that this manual
does not address, contact your dealer or call Clear-Com directly at the factory. Our applications sup­port and service people are standing by to assist you. Thank you for selecting Clear-Com for your
communications needs.

Description

TM

The Clear-Com PL-Pro
trucks, production studio consoles, theatre, live performances, and small TV facilities. It features ex­cellent speech intelligibility in all noise levels and can be tailored to your needs through its programma­ble options.

Selectable two-channel talking and/or listening allows the operator to communicate on either of the in­tercom channels separately or on both at once. The illuminated dual-action talk buttons are electronic
momentary or latching. Monitoring can be done through the headset, the integral speaker, or both at
once. The MS-232 offers both visual and audible call signaling to attract the attention of operators who
have removed their headsets or turned off their speakers. The Remote Mic Kill (RMK) feature provides
the ability to turn off all open mics on Series 500 beltpacks.

MS-232 is a two-channel, one rack space main station ideal for ENG and EFP

The MS-232 can control a paging speaker for studio announcements. A front panel button activates
this function and an associated relay. A balanced program input allows monitoring external audio using
the headset or speaker.

TM

This main station accepts dynamic headsets, such as the Clear-Com PL-Pro

Series. Individual side­tone controls for each intercom channel allow the operator to vary the level of his/her own voice as
heard in the headset and speaker. It also accepts Clear-Com gooseneck panel microphones.

The integral speaker can be turned on or off by a convenient front panel switch. An automatic speaker
dipping circuit will lower the level of the speaker when the announce button, talk buttons or program in­terrupt are activated. This feature helps minimize feedback.

The MS-232 also incorporates a dual-channel program interrupt system (IFB). When activated, one or
more stations can interrupt the program audio to another intercom station or a talent wearing Clear­Com's wired or wireless talent receivers. Clear-Com's stand-alone IFB system can also be connected
to this station.

The MS-232 provides 30-Volt DC power to operate Clear-Com beltpacks and remote stations. This
power is distributed between the two channels, and will support up to 60 headset stations or 20 speaker
stations. Clear-Com's new fail-safe design automatically shuts down the power to a channel when a
short circuit or electronic overload is sensed on that channel. The other channel will continue to oper­ate normally. Once the fault condition is removed, the MS-232's fail-safe circuit will restore power,
even under full load conditions. LED indicators signal a short or overload on either channel.

The MS-232 will operate from any AC line voltage between 90 and 240 Volts AC at 50 or 60 Hz. The
MS-232 installs in a standard 19" equipment rack, using only one rack space. The unitized aluminum
chassis and extra-thick front panel with integral rack ears result in reduced size and a lighter weight
package that maintains legendary Clear-Com ruggedness. Three 3-pin XLR connectors are provided
for connection to each intercom channel.

The MS-232 is compatible with all Clear-Com Party-Line intercoms.

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Clear-Com MS-232 Two-Channel Main Station

QUICK START

1 Unpack the unit and inspect for any damage that may have occurred in shipping. Connect the

proper AC Mains cable.

TM

2 Install the MS-232. (For additional information, refer to the Clear-Com PL-Pro

tion Manual.)
3 Connect the AC to the Mains circuit. Connect the intercom lines.
4 Set the two termination switches on the rear panel to ON.
5 Set the Option switches to the default (up) position.
6 Switch POWER ON. The green power light should be ON and the two red short lights should be

OFF.
7 Set Listen Levels and Sidetones. (Refer to the Listen Level and Sidetone setting topics in the

Operation section of this manual.)
8 The intercom system should now be operating properly.

Read the rest of this manual for further information.

System Installa-

OPERATION

Normal operation of the MS-232 Main Station only requires access to the front panel controls. The
controls located elsewhere on the unit are intended to be set-and-forget in nature. For intercom opera­tion, set the Listen level controls for each channel to the desired level and press the Talk buttons when
talking. If a headset is used, set the Sidetone control for each channel for the desired amount of side­tone in the earphone. If the Panel Mic and Speaker are being used, set the sidetone controls for mini­mum feed-through to the speaker to prevent feedback.

Front Panel

The controls, indicators, and connectors found on the MS-232 front panel are shown in the following
figure and are described by the following text. The numbers in the left column refer to Figure 1.

Figure 1 - Front Panel

1 Talk Buttons: Each channel has an illuminated Talk button for activating the microphone

feed to that channel. Each Talk button has a dual action (momentary or latching) depending
upon how the button is pressed. If desired, the latching function for each channel can be de­feated using the option switches on the rear panel. The following describes the various func­tions of these multi-purpose buttons.

MOMENTARY: Press and hold the Talk button while you are speaking. Release it when
you are finished.

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Clear-Com MS-232 Two-Channel Main Station

LATCHING: Press the button quickly to latch the Talk function. Press the button again to
turn off the Talk function.

TALK INDICATION: The Talk button will illuminate dimly whenever the Talk function is
activated.

CALL INDICATION: The Talk button will flash brightly when a Call signal is received on
that channel.

CALL ON TALK: Each channel can optionally be set to send a Call signal whenever you
press the Talk button. This function is used to activate program interrupts or any other
Call-activated function available on other stations. Option switches on the rear panel will
enable this function.

SPEAKER MUTE: If the front panel speaker is turned on, pressing either Talk button will
reduce the speaker output level to avoid feedback.

The Talk buttons can be labeled to indicate their function. To label the Talk buttons, use the
following procedure:

1 Pull the Talk button straight off.
2 Insert a small flat blade screwdriver into the slot between the cap and the body of the but-

ton and gently twist. This will remove the cap.

3 Remove the square white diffuser from the cap.
4 Insert a 1/2" X 1/2" square of thin paper with the needed description into the cap. Follow it

up with the square white diffuser and press the cap onto the body of the button. Press the
button back into the front panel.

2 Call Buttons: Each channel has its own Call button. Pressing a Call button will send a Call

signal on that channel. All the call lights on that channel will flash. Call signals can also be
sent while talking if required. The Talk button will flash while the Call button is pressed, indi­cating the presence of a Call signal on the line.

3 Tone Alert: An audible tone alert can be enabled to sound when a Call signal is received on

either channel. This can be useful when the operator's attention has been drawn away from
the MS-232 indicator panel. Press the Tone Alert button to alternately enable or disable the
audible tone alert. The green indicator next to this button is lit when the audible Tone Alert is
enabled. When enabled, the Tone Alert will sound when a Call button on a beltpack or station
is pressed. The Tone Alert will not sound if a Call signal is originated at the MS-232 station.
The level can be adjusted by the control on the rear panel (4).

5 Listen Level Controls: Each channel has a separate Listen level control. Turn these con-

trols to set the listen level you need on each channel. Turn the control completely counter­clockwise to silence a channel.

6 Sidetone Controls: Each channel has a Sidetone Null control. Sidetone is the level of your

own voice that you hear while talking on the intercom. Setting a comfortable level of sidetone
will ensure that the intercom line sounds alive and also helps you modulate your voice relative
to other voices on the line.

Typically, different Sidetone Null settings are needed depending upon whether you are using
the gooseneck panel microphone along with the speaker or not. Use one the following proce­dures to correctly set the Sidetone level controls.

Sidetone Adjustment Procedure for Gooseneck Microphone with Speaker turned on:

1 Turn off the Party Line Link (A+B) switch.
2 Turn the Level control for Channel B all the way down. Set the Level control for Channel

A to a comfortable level.

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Clear-Com MS-232 Two-Channel Main Station

3 Press the Channel A Talk button and speak into the microphone while turning the Sidetone

Null control for Channel A slowly back and forth. There should be a point where your
voice (and any accompanying acoustic feedback) disappears. This is the null point.

4 Repeat this procedure for Channel B by turning the Channel A Level control down and ad-

justing the Channel B controls.

Sidetone Adjustment Procedure for Headset:

1 Turn off the Party Line Link (A+B) switch.
2 Turn the Level control for Channel B all the way down. Set the Level control for Channel

A to a comfortable level by having someone talk to you from another station.

3 Press the Channel A Talk button and speak into the microphone while turning the Sidetone

Null control for Channel A slowly back and forth until you hear your voice at a comfortable
level in the headset.

4 Repeat this procedure for Channel B by turning the Channel A Level control down and ad-

justing the Channel B controls.

7 Program ON-OFF-INTRPT Switches: The Program ON-OFF-INTRPT switches are used to

manually or automatically control program audio feed into the intercom lines. The settings are
as follows:

ON: The channel will receive program audio when the switch is set to ON. The audio level
for each channel can be adjusted with the Program Level trimpots as described in the
following paragraph.

OFF: The channel will not receive program audio when the switch is set to OFF.
INTRPT: Pressing the Talk button will interrupt the program when this switch is set to

INTRPT.

8 Program Level Controls: Adjust the Program Level controls to set the program audio level

heard on the intercom. There are three Program Level controls. The Program Level knob to
the left of the Speaker On-Off switch adjusts the level of program heard in the headset or
panel speaker.

The program levels heard on each intercom channel line can be individually adjusted, but this
is intended to be a one time setting made when the MS-232 is set up. This is done using the
screwdriver level adjustment trimpots adjacent to the Program ON-OFF-INTRPT switches on
Channels A and B. Set the Sidetone Null controls and the Program Level knob fully counter­clockwise when adjusting the individual channel Program Level trimpots. After the Program
Level trimpots are properly adjusted, use the procedure listed in the Sidetone Controls sec­tion on this page to set the sidetone level.

: Do not force the trimpots past their stop points. This will damage them.

NOTE

9 Party Line Link (A+B) Switch: The Party Line Link (A+B) switch is used to combine both in-

tercom channels into one, for example, for rehearsals. When this switch is set to the ON posi­tion, the green lamp directly above the switch will light, and all of the stations on the B channel
will be moved onto the A intercom line. This will allow communication between everyone on
both channels at once.

In this mode, the Channel B controls and switches will be inactive. Since the wiring for the B
channel has been now added to the A channel, the Sidetone Null control for Channel A may
require some readjustment.

10 Speaker ON/OFF Switch: The Speaker ON/OFF Switch turns the front panel speaker on or

off. This switch does not affect whether the Tone Alert is heard through the speaker. The
speaker volume will automatically dip whenever the panel or headset microphone is on.

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Clear-Com MS-232 Two-Channel Main Station

11 Remote Mic Kill Switch: The Remote Mic Kill (RMK) switch will turn off the Talk function of

every beltpack on channels A and B. If the Talk functions of a large number of beltpacks have
inadvertently been left activated, incidental noise and talking can make it difficult or impossi­ble to communicate on the party line intercom. The Remote Mic Kill switch can be pressed to
quiet the line in this situation. Those needing to communicate can then set their Talk functions
ON as needed.

: The Remote Mic Kill switch can only function if the MS-232 Main Station is

NOTE
powering all of the stations in the system. The switch momentarily interrupts power
to the other beltpacks and stations in the system. If there are other power supplies or
main stations in the system, then the Remote Mic Kill switch cannot interrupt power
and therefore cannot work.

12 Mic Select Switch: Set the Mic Select switch to select whether the panel microphone or the

headset microphone is active.

13 Panel Mic Gain: This control is located on the underside of the MS-232 chassis. It may be

used to increase or decrease the sensitivity of the panel microphone. It has no effect on the
sensitivity of the headset microphone. Use a small screwdriver to turn the control clockwise to
increase sensitivity or counterclockwise to decrease sensitivity.

14 Announce: Press the Announce button to make stage or PA system announcements. It di-

rects the audio from the selected headset or panel microphone to the Annc Out rear panel
connector and activates the Announce Relay. Simultaneously, if the program audio feed to
the Announce Output is enabled, it is interrupted by the announcement. Program audio feed
to the Announce Output is selected by setting jumper JP2 on the Main board to the ON posi­tion. Optionally, pressing the Announce button can also disconnect the selected headset or
panel microphone audio from the intercom line(s). This option is controlled by the Interrupt
Announce option switch.

19 Headset Connector: The headset connector is located on the front panel. All Clear-Com

headsets are recommended for use with the MS-232. The following is a description of the
characteristics of a suitable headset:

Mic Type --- Dynamic; 150 to 250 ohms impedance; -55 dB output level
Headphone --- Dynamic; 50 to 2000 ohms impedance

The wiring of the headset is to be as follows:

Pin 1 --- Mic common
Pin 2 --- Mic hot
Pin 3 --- Headphone common
Pin 4 --- Headphone hot

The mic and headphone wiring in the headset cord must be individually shielded. Do not
connect Pins 1 and 3 together. Headset extension cords or headset "Y" cables are not rec­ommended because they will increase crosstalk between channels.

18 Panel Mic Connector: Clear-Com recommends the GM-9 and GM-18 plug-in panel micro-

phones for use with the MS-232. The GM-9 is 9 inches long and the GM-18 is 18 inches long.
The microphone is an electret type. The 1/4 inch phone jack on the microphone mates with
the Panel Mic receptacle on the front panel of the MS-232.

To install a GM-9 or GM-18 microphone, use the following steps:
1 Check and unscrew the set screw in the mic mounting flange to make sure it is clear of the

threads in the bushing.

2 Screw the microphone into the bushing hand tight.
3 Turn the set screw on top of the mic mounting flange clockwise to lock the microphone in

place.

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Clear-Com MS-232 Two-Channel Main Station

26 Party Line Link (A+B) LED: This green LED is lit when the Party Line Link (A+B) switch is

ON, to provide a visual indication that party line Channels A and B are linked together.

27 Tone Alert LED: This green LED lights when the Tone Alert function is enabled. Tone Alert

is an audible indication that a Call signal is active. Toggle the Tone Alert function ON or OFF
using the Tone Alert button.

28 Power LED: This green LED lights when the MS-232 is receiving AC power and the power

switch on the rear panel is turned on.

29 Short LEDs: There is one red LED for Channel A and one for Channel B. These LEDs light

when the MS-232 senses a short or overload on the associated channel. When the fault is re­moved, the MS-232 will automatically reset and the LED will go out.

Rear Panel

The controls and connectors found on the MS-232 rear panel are shown in the following figure and
briefly described by the following text. The numbers in the left column refer to Figure 2.

Figure 2 - Rear Panel

4 Tone Alert Volume Control: This control adjusts the volume of the Tone Alert sound. This

is normally adjusted when the system is set up and there should be no need to adjust it in nor­mal operation.

15 Option Switches: Eight Option switches are provided on the rear panel. They should be

configured when the system is set up, but are not changed in normal operation. The default
position of the switches is in the OFF (up) position. The function of each switch is as follows:

1 MOM TALK A: Setting the Momentary Talk A switch to the ON position will disable the

latching function of the Channel A Talk button. In this mode, the Talk button must always
be held in continuously while the operator is talking on Channel A.

2 MOM TALK B: Setting the Momentary Talk B switch to the ON position will disable the

latching function of the Channel B Talk button. In this mode, the Talk button must always
be held in continuously while the operator is talking on Channel B.

3 CALL ON TALK A: If the Call On Talk A switch is set to the ON position, a Call signal will

be placed on Channel A whenever the Talk function is activated. This can be used to acti­vate any Call activated functions available on other stations.

4 CALL ON TALK B: If the Call On Talk B switch is set to the ON position, a Call signal will

be placed on Channel B whenever the Talk function is activated. This can be used to acti­vate any Call activated functions available on other stations.

5 INTRPT ANNC: If the Interrupt Announce switch is set to the ON position, pressing the

Announce button will disconnect the microphone from the intercom line(s). This will allow
announcements to be made without being heard over the intercom channels.

6 INTRPT EXT IFB: When the Hot Mic output is connected to Clear-Com's IFB System and

the Interrupt External IFB switch is set to the ON position, pressing a key on the IFB

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Clear-Com MS-232 Two-Channel Main Station

System will disconnect the selected headset or panel microphone from the intercom
line(s). This allows the MS-232 microphone to be used to cue talent without affecting in­tercom line communication.

7 LONG LINE A: If a long cable run on Channel A is unavoidable and approaches 1,000

feet or more, set the Long Line A option switch to the ON position. The ability to set a
sidetone null on Channel A depends upon properly setting this switch.

8 LONG LINE B: If a long cable run on Channel B is unavoidable and approaches 1,000

feet or more, set the Long Line B option switch to the ON position. The ability to set a
sidetone null on Channel B depends upon properly setting this switch.

16 Termination Switches: These switches provide switchable terminations for channels A and

B. In most systems, both terminations on the MS-232 should be in the ON position (default
setting). The fundamental concept of Clear-Com Party-Line intercom is that all channels are
terminated in one location, preferably at a main station or power supply. The termination
switches on the MS-232 rear panel should be set to the OFF position only if the channel is ter­minated by another main station or power supply in the system. If there are no other main

stations, power supplies, or other terminations on the line, set the rear panel switches
labeled TERM A and TERM B to the ON position.

: All intercom lines must be terminated only once, whether they are used or not.

NOTE
Never "double-terminate" a line.

17 Power Switch: The power switch can be used to turn AC power to the MS-232 on and off.

When in the ON position, the Power LED on the front panel will be illuminated.

20 AC Power Connection: An IEC type 320 connector is provided to interface to the appropri-

ate AC power cord to be used. Voltages from 90 to 240 VAC at 50 or 60 Hz are acceptable.
The MS-232 will automatically adjust for the power applied, so there are no manual switches
to set power line voltage or frequency.

21 Intercom Line Connection: The MS-232 contains three 3-pin male XLR connectors for each

intercom line. These connectors are wired in parallel. Any single-channel station or channel
of a multi-channel station connected on a line plugged into Channel A of the MS-232 will be
"party-lined" with all the other stations on that channel. In a multi-channel system, the goal is
to assign specific people to the correct group, i.e. the other people they need to be in contact
with the most. This is particularly important when the party line users are on a single-channel
beltpack or station; less so if they are on multi-channel stations. The pinout of the intercom
connectors is as follows:

Pin 1 --- Ground (Shield)
Pin 2 --- Power (+30 VDC)
Pin 3 --- Audio

22 Program Input: A 3-pin XLR female connector provides the main program input to the sta-

tion. Program can be fed to the headphone or speaker as well as to either or both of the inter­com channels. The level to the speaker or headphone is controlled by the Program Level
control. The Program ON-OFF-INTRPT switches control whether each intercom channel re­ceives program audio. The program audio levels on each intercom channel can be adjusted
using the individual Program Level trimpots. The Program Input accepts a balanced or unbal­anced line-level audio signal from -20 dBv to +10 dBv. An option is to feed program audio to
the Announce Output. This is selected by setting jumper JP2 on the Main board to the ON po­sition. When this option is selected, a 0 dBv signal on the Program Input will produce a 0dBv
signal on the Announce Output.

The pinout of the Program Input connector is as follows:

Pin 1 --- Ground (Shield)
Pin 2 --- + Signal
Pin 3 --- - Signal

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