Production Intercom MS 301

3-Circuit Intercom Master Station w/ IFB Functions

Overview

The MS301 is our top-of-the line Master Station and includes every practical feature you’ve suggested over time. It combines microprocessor control with an internal linear power supply and analog audio circuitry, all in a 1U cabinet.

The MS-301 is a full featured main station with integral high capacity power supply. It has the capacity to control three independent communications circuits. The single rack unit high (1U: 1.75”) cabinet is available with either plain side panels (standard) or available rack-mount side panel.

 The MS-301 has three independent communications circuits labeled A, B, and C. The operator may communicate with stations connected to any or all of the circuits by enabling the circuit ON switches. The SmartSwitch feature allows the circuit enable switches to be used automatically in either push on/push off or PTT (Push To Talk) modes.

Normally, the three circuits remain independent, and stations connected to one cannot speak to stations connected to the others. During rehearsals, or other activities where a more global common communications circuit would be desirable, switching the LINK function on can circuits A and B together, or link all three circuits together. This allows an operator at the MS-301 to cue or guide two or three separate groups of personnel who are otherwise independent. A standard headset may be used with the MS-301, or, if desired, a gooseneck microphone (LSM-x, sold separately) may be plugged into the front panel headset jack, and the MS-301 can be used as a fully duplex hands-free communications station utilizing its internal wide-range speaker. The sidetone null control can be adjusted to effectively eliminate any possibility of ringing and feedback. The operator can monitor any circuit at any level, while communicating with any, all or none of the circuits. Individual volume faders provide for a complete custom mix. A front panel switch diverts the output of the headset (or gooseneck) microphone to a rear panel 600 ohm balanced output (both XLR and ¼” TRS), permitting paging through a remote paging amplifier, eliminating the need for a separate microphone for this purpose. This output may also be sent to an audio console. To activate the remote amplifier, a pair of normally open contacts, accessible on the rear panel, are closed as long as the Page key is pressed. An external auxiliary program input is provided. A trim switch on the rear panel allows connection with either Mic level (nominal -44dBm) or line level (-24dBm) sources. The connector allows for either XLR or ¼”, balanced or unbalanced inputs. These allow external sources such as program feeds, run-of-the-show relays, paging announcements or other background information to be mixed onto the communication circuit(s). Individual faders allow adjustment of the level of auxiliary program material to each of the three circuits. When an operator at the MS-301 activates the headset or gooseneck mic, he can either talk over the program material or interrupt it. A unique feature of the MS-301 automatically fades the program material down to zero over a one second interval, while bringing the MS-301 mic level up to full.

The effect is pleasant and non-alarming to a listener on the circuit. When the mic switch is deactivated, the program material fades up to full over a one second interval. This is especially useful when broadcasting with guest talent. The interruption can be set to instantaneous, if so desired. The internal power supply provides power for up to 66 beltpacks connected to the circuits. Power is well regulated at 24 volts DC and will automatically adjust down during periods of line voltage brownout or high loading with powered speakers or other equipment. Short circuit protection and current limiting prevent component damage in the event of misconnection or cable failure. The toroidal transformer, coupled with linear regulators ensure noise-free operation under all conditions. The MS-301 has a quiet built-in fan that turns on automatically when needed to cool the unit. Front panel indicators show the status of all circuits and allow an operator to quickly address a circuit problem. Each circuit has a characteristic impedance of 200 ohms at audio frequencies, allowing many beltpacks to connected together without significantly changing the circuit performance. The termination networks are automatically removed and inserted during circuit linking to ensure a constant impedance for all circuits. The termination networks may also be manually removed by setting a switch on the rear panel, if desired. This may be useful when using an adjunct network, or if interfacing with a larger communications system.

Key Features

• Three circuits rather than the usual two.

• Each circuit can be intercom or IFB in any combination.

• Circuits are linkable (A + B) or (A + B + C) with auto termination impedance adjustment.

• Each circuit’s termination can be lifted via rear panel DIP switches.

• Independent level control of program audio output for each circuit with an LED VU meter for each.

• Mic switch on each circuit can be tapped for locking or held and released for momentary.

• Internal power supply is linear (except for microprocessor functions) with 2.4A continuous output.

• Toroidal transformer with extensive monitoring and auto-control of overload and heat considerations.

• Full duplex, hands-free operation, even in moderately noisy environments. (with optional gooseneck mic.)

• Paging output (balanced and isolated) on rear panel activated by front panel momentary button.

• Dry contacts on rear panel also closed by page button

• Front panel 4-pin XLR may be used for gooseneck mic. or headset.

• Gooseneck or headset mic. may be dynamic or electret. Lighted front panel switch sets choice.

• Front panel green LED indicates presence of 24VDC across the three circuits.

• Three front panel flashing red LEDs report trouble status of each circuit. Other circuits are not affected.

• System resets when the problem is repaired.

• While switching is all electronic, the audio paths remain analog providing comfortable long-term listening.

• A front panel button initiates ‘Override’ which overrides front panel controls on LS2 and LS3 loudspeaker stations, restoring preset volume and status.

Specifications

• Current draw (at 120VAC): 0.14A (no load), 1.05A @2.4A DC out

• Power output: 24 volts DC regulated @ 2.4A continuous

• Line termination: DC: 5KW, 50 Hz-20 KHz: 200W

• Transducer impedances: Mic: 200W dynamic or 1.2kW electret, Earphone: 200~600W

• Aux. input: Mic level: (-44dBm) 48KW, Line level (-24dBm): 1KW

• Size (excluding ears) : 17” width x 9.5” depth x 1.75” height (432 x 241 x 44.5 mm)

• Weight: 9.8lbs. 4.5Kg

Front Panel Features:

1. Main power switch: Illuminated LED indicates AC voltage present.

2. Headset/Handset/Gooseneck Mic input: Accepts standard dynamic or electret mic headsets / handsets / gooseneck microphones terminated with 4pin female XLR.

3. Intercom circuit power indicators: Top LED indicates 24VDC present in unit. Individual channels lit Green when in normal operating conditions. Flashing Red indicates a short circuit. Solid Red indicates overheating of power supply has occurred, and circuit has shut down.

4. Override activation button: Latching button sends signal to override equipped products to return them to preset volume levels. Lit LED indicates override is active.

5. Mic select switch: Allows user to select between dynamic or electret mic input into Headset / Handset input. Lit LED indicates Electret Mic setting Non Illuminated LED indicates Dynamic Mic setting..

6. Talk circuit volume control: Allows user to balance “local’ listen levels of each circuit individually. This control only effects levels at this station, and does not effect others on the talk circuit.

7. Mic control button: Controls mic operation for assigned talk circuit. Button has both momentary and latching function. Press and hold while talking, release when done talking, for momentary operation. Press quickly for latching operation. Illuminated switch indicates an active Mic in either mode of operation.

8. Signal Button: Used to signal or “call” other users on assigned talk circuit. Non latching button illuminates signal LEDs both locally and remotely. When sending or receiving a signal the LED will start to flash if button is depressed for more than .25 seconds. The signal button will also trigger any Blazon strobe units to flash 4-5 times as a visual cue to users not closely monitoring their station.

9. Link control switch: 3 position toggle for linking intercom talk circuits. Up position combines circuit A and circuit B into a single talk circuit. Middle position allows all 3 circuits to operate Independently of each other. Down position combines all 3 circuits into one single talk circuit.

10. Page output button: Non-latching button for connecting to a house paging system. When the button is depressed it simultaneously closes a dry contact and opens the users mic to a 600W balanced audio output located on the back panel.

11. Sidetone control: Recessed rotary potentiometer used to adjust the level of the users own voice locally. This control will only effect the level locally, and will have no effect on other users in the talk circuit. May also be used as a “Nulling Pot” to help eliminate feedback when using with a gooseneck Mic and speaker. The zero setting of this control is typically near the 12:00 position.

12. Program input selection: 3 position toggle allows user to select between 4 variables of program input. In the upper posi tion the program material will be present in assigned talk circuit with the ability to talk over the input. In the middle position the program input is not present in the assigned talk circuit. In the lower position the program input is present in the talk circuit, with the ability to interrupt when speaking. The interrupt feature is user defined, with a DIP switch on the rear panel, for instant interrupt, or interrupt with fade.

13. Program level control and indicators: A recessed rotary potentiometer is used to adjust the program material volume for each assigned circuit. In addition a LED VU meter is available for visually monitoring levels while not listening to the circuit. The LEDs confirm signal present, and warn of audio clipping.

14. Built in speaker controls: A 2 position toggle for turning the built in speaker on and off. Rotary volume knob for adjust ing desired speaker listen levels. These controls effect the built in speaker only, and have no effect on the users headset or handset.

Rear Panel Features:

1. Dip Switch : 8 position Dip switch for ser defined functions

*1. IFB Functon- Down will fade out program input and fade in Mic when Mic is activated.Up will cut program input instantly and replaace with Mic input instantly when Mic is activated.

*2-4. are not active at this time.

*5-7 will activate and deactivate the 200 Ohm termination circuit for each talk circuit.

*8. Changes Program input impedance.Down is line level (+4db), Up is Mic level (-20db)

2. Female 9 pin D sub: Used for interconnection to/from MSM300

3. Male 2 pin terminal : Dry contact associated with page out feature.

4. Paging Output: Combination 3 pin female XLR 1/4" phone out.

5. Program Material Input: Combination 3 pin female XLR 1/4" phone input.

6. Talk circuit Out: 3 pin male XLR. 2 per circuit .Pinout : 1=Shield,2=24vdc 3=Audio

7. Voltage Selector Switch: Use to select between 115VAC or 220VAC power source

8. AC Line Input/Fuse Holder: Fuses -100/120V 2A/250V 220/240V 1A/250V

Sample Diagram: