User Guide Issue 2, January 2020 This User Guide is applicable for serial numbers: M47A-01151 and later with software version 1.3 and higher Copyright © 2020 by Studio Technologies, Inc., all rights reserved www.studio-tech.
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Table of Contents Revision History ............................................................ 4 Introduction ................................................................... 5 Installation ..................................................................... 10 Configuration ................................................................ 16 Advanced Configuration ............................................... 17 Operation ......................................................................
Revision History Issue 2, January 2020: 1. Documents addition of feature that allows DC power on pin 3 of party-line interfaces to be disabled. (Applies to software version 1.3 and higher.) Issue 1, September 2014: 1. Initial release. Issue 2, January 2020 Page 4 Model 47A User Guide Studio Technologies, Inc.
Introduction The Model 47A is designed to interface 2-wire full-duplex party-line (PL) intercom circuits with 4-wire audio circuits associated with matrix intercom systems. Other specialized audio system interfacing applications can also be supported. The Model 47A provides two independent fullfeatured 2-channel interfaces. Each interface contains two hybrid circuits which include automatic nulling capability.
supplies such as the RTS PS20. This DC power, normally 30-32 volts, provides energy for connected devices such as user stations or beltpacks. In this type of application the Model 47A is configured to operate in its external 2-wire power source mode. In this mode the Model 47A’s circuitry maintains the required high-impedance load and, as in all cases, draws no power from the party-line circuit.
Remote sports broadcast applications are especially sensitive to this requirement. The Model 47A’s sophisticated auto nulling function uses analog circuitry under microprocessor control to achieve significant trans-hybrid loss. This return-loss “null” is achieved by making a series of adjustments to account for the resistive, inductive, and capacitive conditions that are present on the connected 2-wire partyline circuit.
setup the meters are invaluable in helping to confirm that the nominal level DIP switch settings have been properly made. During normal operation the meters offer rapid confirmation of audio signal flow in and out of the unit. Additional LED status indicators are also provided, offering a clear view of the 2-wire DC power and auto null functions.
Simple Installation The Model 47A uses standard 3-pin XLR connectors to allow convenient interconnection in most broadcast and general audio environments. For flexibility, access to the 2-wire party-line intercom interfaces can be made using the connectors provided on both the front and back panels. In permanent installations the back-panel connectors will typically be utilized.
out that in many applications only a small number of user devices, such as beltpacks, are typically connected to 2-wire party-line intercom circuits. But power on both pins 2 and 3 of each interface was necessary for compatibility with SAP panel applications. By adding two DC power sources to each of the Model 47A’s 2-wire interfaces, the need for external intercom power supplies could often be eliminated.
analog line-level audio sources to be connected. The source for these signals will typically be ports on a matrix intercom system. It’s also possible that the signals will come from other devices, such as a fiber-optic-based audio transmission system. The 4-wire input circuitry is balanced, capacitor coupled, transformer isolated, and has an impedance of 13 k ohms. The line inputs are compatible with signals that have a nominal level of 0, +4, +6, or +8 dBu.
and the line inputs. The 4-wire line outputs are capable of driving inputs that have impedances as low as 600 ohms, however connecting to loads of 2 k ohms or greater is preferred. The line outputs are connected by way of 3-pin male XLR connectors which are located on the Model 47A’s back panel. Refer to Figure 1 for a detailed view. The mating connectors (females) should be prepared so that signal high (+ or hot) is expected on pin 2. Signal low (– or cold) should be expected on pin 3.
The most direct method is to prepare the female XLR mating connectors so that common is on pin 1, power is on pin 2, and audio is on pin 3. With this connection scenario only audio channel 2 (the channel associated with pin 3 of the Model 47A’s 2-wire PL intercom interface connectors) will be utilized. Pin 2, the Model 47A’s audio channel 1, will only be used for connecting DC power to the connected singlechannel devices.
User intercom devices compatible with this 24 kHz “mic kill” signal include RTS TW-Series beltpacks such as the BP325. The opto-coupled remote control inputs are designed for direct connection with 3.3 and 5 volt DC logic signals. An internal 475 ohm resistor, in series with each opto-coupler’s photodiode, acts to limit the current flow. Signals of up to 32 volts DC can be safely connected as long as the current is limited to 20 mA maximum. If necessary, an external resistor can serve to limit the current.
It’s important to ensure that the source of the remote control signals can meet the Model 47A’s logic state and timing requirements. The Model 47A recognizes an idle remote control input as one that has no current flowing through it. An active remote control input is one that has current flowing through it for a minimum of 30 milliseconds. A special case arises when the auto null button operating mode has been set to independent.
As soon as AC mains power is applied the Model 47A will begin its power-up sequence. As a “boot up” indication the power LED and each of the status LEDs will momentarily light. After the sequence has completed the power LED will again light and remain lit. The unit is now fully functional. Configuration For the Model 47A to support the needs of specific applications a number of operating parameters must be configured.
Studio Technologies, Inc. can be directly connected. There’s also no problem connecting single-channel intercom beltpacks or user stations. 2-Wire Nominal Audio Level DIP switch 2 allows adjustment of the nominal audio level for the two 2-wire party-line channels associated with interface 1. When the DIP switch is in its off (down) position the nominal level is –14 dBu. This level is compatible with intercom beltpacks from manufacturers such as Clear-Com.
Auto Terminate The auto terminate function is designed to ensure that each 2-wire-to-4-wire interface circuit remains stable under most operating conditions. Specifically, 200 ohm impedances are automatically applied to both pins 2 and 3 of a Model 47A 2-wire party-line interface when that interface is configured for external power and no external source of intercom power is detected on pins 2 or 3.
Auto Null Button One pushbutton switch is associated with each of the Model 47A’s two interface circuits. An advanced configuration parameter allows selection of the button’s operation. The choices are dual auto null and independent auto null. When dual auto null is selected a single tap of one of the two front-panel pushbutton switches initiates a routine that begins with channel 1’s auto null sequence taking place followed immediately by channel 2’s auto null sequence being performed.
DC power source. (This scenario would be the same as provided by the Studio Technologies’ Model 46A Intercom Interface.) For example, if a single-channel Clear-Com party-line intercom circuit is directly connected to a Model 47A then the DC power present on pin 3 would cause the call light function on any connected Clear-Com user beltpacks to be enabled.
Operation Technician intervention is typically not required during normal Model 47A operation. The unit is designed for continuous operation with no routine maintenance necessary. Activating the auto null functions may be warranted should connected user devices or wiring associated with the 2-wire party-line intercom be changed. Upon power-up the Model 47A will go through a short initialization sequence before normal operation will begin.
If the Model 47A’s 4-wire nominal levels are set correctly but the meters still reflect sub-optimal levels, the issue may be related to incorrect settings on the equipment connected to the 4-wire inputs and outputs. It’s possible that although a connected 4-wire device’s nominal level matches the Model 47A’s level setting, its actual nominal level may be significantly different.
level greater than approximately 18 volts DC on pin 2 will cause the pin 2 status LED to light. A level greater than 18 volts DC on pin 3 will cause the pin 3 status LED to light. The author is aware that user intercom devices almost always draw power from pin 2 rather than pin 3. However, in many broadcast applications power is provided on all intercom paths so that flexible channel assignments can be made.
Model 47A’s 2-wire connectors will result in a continuous cycle of 4-seconds on (three seconds for start up and one second for detection) and 6-seconds off. Auto Null Each of the Model 47A’s 2-channel interfaces has circuitry to automatically null the two 2-wire-to-4-wire interfaces. Normally this process is performed at the time of initial Model 47A configuration but there’s no reason why auto nulling can’t be initiated anytime one desires.
the automatic “mic kill” signal will apply to many user devices it may not apply to all. Muting microphones is significant as obtaining a “deep” null requires that no extraneous signals be present on the intercom circuit. Advanced Operation The Model 47A allows several of the operating parameters to be configured to meet the needs of specific applications. The following paragraphs provide details about the auto terminate and factory test modes.
operation DIP switch 4 should remain in its off (down) position. When DIP switch 4 is in its on (up) position factory mode is active (enabled). Enabling this mode will result in the following operating condition: during an auto null sequence the associated 4-wire output channel will remain active. This will allow the tones associated with the nulling process to be present on the 4-wire output. While not appropriate during actual Model 47A use, it is interesting to “hear” the nulling process take place.
To display the Model 47A’s software version is very simple. From the powered-down state, press and hold the auto null button associated with interface 1. Apply mains power while continuing to press the button. The normal power-up sequence will occur and then one LED will be lit in the column associated with FROM 4-wire channel 1 of interface 1 and one LED will be lit in the column associated with TO 4-wire channel 1 of interface 1.
Specifications General Audio: Frequency Response: ±2 dB 100 Hz to 8 kHz Distortion (THD+N): <0.
Appendix A Interfacing RTS® Matrix Intercom Systems with the Model 47A Interface ADAM™ Matrix Intercom System Analog Ports to Model 47A Interface RVON-I/O I/O Connections to Model 47A Interface Model 47A User Guide Studio Technologies, Inc.
Appendix B Interfacing Riedel® Artist™ Matrix Intercom System Analog Ports with the Model 47A Interface Issue 2, January 2020 Page 30 Model 47A User Guide Studio Technologies, Inc.
Appendix C Interfacing Clear-Com® Matrix Intercom System Analog Ports with the Model 47A Interface Model 47A User Guide Studio Technologies, Inc.
CI RCUI TRY I DENTI CAL FOR I NTERFACES 1 & 2 2 ON/ OFF CONTROL FROM MCU BAND- PASS FI LTER 10K: 10K 4- WI RE I NPUT I NTERFACE 1 CHANNEL 1 0/ +4/ +6/ +8dBu ( XLR- F) 100Hz LEVEL CONTROL BUFFER ON/ OFF CONTROL FROM MCU 200 OHM I MPEDANCE GENERATOR BI - LATERAL CURRENT SOURCE TO MCU A/ D I NPUT 3 LOCATED ON FRONT PANEL 1 2- WI RE PL I NTERCOM CI RCUI T I NTERCOM POW ER SOURCE 30V, 8kHz 315mA MAX, PI N 2 & PI N 3 - 14/ - 10dBu ( XLR- M) 2 2 14dB PAD 3 3 DATA FROM MCU 1 LOCATED ON BACK P
EEPROM MEMORY AUTO NULL I NTERFACE 1 MI CROCONTROLLER I NTEGRATED CI RCUI T ( MCU) AUTO NULL I NTERFACE 2 CONFI GURATI ON SWI TCHES TYPI CAL OF 12 + 1 - REMOTE CONTROL I NPUTS* STATUS LEDS TYPI CAL OF 9 + 2 DATA SI GNALS TO DEVI CES A/ D I NPUTS + 3 - TONE1- 1 SI NE- WAVE * CONNECTOR LOCATED ON PRI NTED CI RCUI T BOARD ASSEMBLY DUAL 4X1 SWI TCH TONE GENERATOR TONE2- 1 TONE1- 2 TONE2- 2 CH1- 1 FULL- W AVE CH2- 1 LEVEL CH1- 2 DETECTOR CH2- 2 AC MAI NS I NPUT 100- 240V 50/ 60Hz OPERATI ON I E
