Handbook of Intercom Systems Engineering

1 38109-977 Rev. 4 Handbook OF Intercom Systems ENGINEERINGFIRST EDITIONThe Fine PrintThe Handbook of Intercom Systems Engineering , first edition, Copyright 2007 by Telex Communica-tions, Inc. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, electronic or mechanical, including photocopying and recording, or by any information storage or retrieval system without the prior written permission of Telex Communications, Inc., unless such copying is expressly permitted by federal copyright copying inquires to:Bosch Communications SystemsTelex Communications, : Intercom Department12000 Portland Ave SBurnsville, Minnesota 55337 USAI nformation contained in this work has been created or obtained by Telex Communications Inc.

2 From sources believed to be reliable. However, Telex Communications, Inc. does not guarantee the accuracy or completeness of the information published herein nor shall Telex Communications Inc. be liable for any errors, omissions, or dam-ages arising from the use of this information. Telex Communications, Inc. is not attempting to provide professional services through the publication of this book, but rather intends only to provide information. If such professional services are necessary or desired, users of this book should seek such professional OF CONTENTSP reface- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -3 About the Authors - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -5 Intercoms An Overview - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -1 Introduction.

3 1 Party-Line Systems ..1 Matrix Systems ..2 Wireless Systems ..2 Accessories ..3 Before We Begin ..5 IFB ..5 ISO ..6 Tally..6 The Rest Of The Book ..6 Introduction to Party-LineIntercom Systems - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -7 Introduction ..7 Some Definitions ..7 Party-Line (PL) Systems / Conference Line Intercom Systems ..7 Two-Wire ..7 Balanced Line ..8 Full Duplex ..8 Decibel (dB) ..8 Beltpack ..8 Biscuit ..8 Main Station ..8 Master Station ..8 Sidetone ..8 Crosstalk.

4 8A Short History ..8 Present Day Systems and Manufacturers ..9 system Components and Their Function .. 10 Belt Pack Headset User Station Functional Description.. 11 Speaker User Station Functional Description .. 12 Master Stations .. 12 Some Technical Notes About The Stations Above .. 12 How Each system Works .. 13 system Powering .. 14 Headset User Stations.. 14 Speaker User Stations.. 14 Master Stations .. 15 Cabling .. 15 Outstanding Features of Each system .. 15 Call Lights .. 15 Limitations of Each system .. 16 Summary .. 16(Some Definitions) .. 16(A Short History).

5 16(Present Day Systems and Manufacturers) .. 16( system Components and Their Function) .. 17(How Each system Works) .. 17(Outstanding Features of Each system ) .. 18ii(Limitations of Each system ).. 18 Design of Party-Line Intercom Systems - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -21 Overview .. 21 Defining And Meeting Your Needs .. 21 Application 1 Generic Single Channel Systems .. 21 Audiocom Party-Line Intercom Equipment Listing #1 .. 22 Clear-Com Party-Line Intercom Equipment Listing #1 .. 23 RTS TW Party-Line Intercom Equipment Listing #1.

6 24 Application 2 Two-Channel system : TV, School, Cable .. 24 Audiocom Party-Line Equipment Listing #2 .. 25 Clear-Com Party-Line Equipment Listing #2 .. 25 RTS TW Party-Line Equipment Listing #2 .. 26 Application 3 Theater system .. 26 Audiocom Party-Line Equipment Listing #3 .. 27 Clear-Com Party-Line Equipment Listing #3 .. 27 RTS TW Party-Line Equipment Listing #3.. 27 Application 4 Training Systems .. 28 Audiocom.. 28 Clear-Com .. 29 RTS TW .. 30 Application 5 Medium system for Television .. 31 The IFB system (One Way Communications system ) .. 32 How an IFB Works.

7 32 Studio and Some Field Applications .. 32 Field Application, Sports .. 32 Field Application, ENG (Electronic News Gathering) .. 33 Connecting (Interfacing) to Other Communications Systems .. 33A Typical Interfacing Problem .. 34 Interfacing Issues .. 34 Modes .. 35 Level Problems .. 35 Signal / Data Conversion .. 35 Call Light .. 35 Data.. 35 Interfacing Practice .. 36 Interfacing Television Camera Intercom Systems to TW Systems .. 36 General Camera Configuration Information for Television Cameras (except ENG units) .. 36 The Problems in Interfacing to Cameras.

8 36 Alternatives for Interfacing to Television Cameras .. 36 Some Practical Considerations .. 37 Headset Cable Lengths .. 37 Headphone Impedances .. 38 Wiring Practices/Workmanship Standards .. 38 Unbalanced vs. Balanced .. 38 Extended Range On Part Or All Of The system .. 38 Cable Considerations .. 39 Crosstalk .. 39 Crosstalk Through A Common Circuit Ground .. 39 Crosstalk Through A Mutual Capacitance Of Two Conductors .. 39A Low Crosstalk Approach To Interconnection.. 39 Distances/Conductor Sizes/Distributed vs. Central Connection .. 39 system Current/ system Capacitances/Loading.

9 40 Temperature Range Consideration .. 40 Cooling Requirements .. 40 Moisture / Contamination Protection .. 41 Magnetic Fields: Hum Problems .. 41 SUMMARY .. 41(Defining and Meeting Your Needs) .. 41(The IFB system (One Way Communications system )) .. 42iii(Connecting (Interfacing to Other Communications Systems )).. 42(Some Practical Considerations) .. 42 Introduction to Matrix Intercom Systems - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 45 Introduction .. 45 Definitions.. 45 History of Matrix Intercoms.

10 47 Modern Day Matrix Intercoms .. 52 Special Considerations .. 53 Advantages .. 53 Size .. 53 Configurability .. 53 Types of Communications Supported .. 53 Ancillary Functions .. 54 Basic Ancillary Functions via GPI/O General Purpose Input / Output .. 54 More Complex Ancillary Functions .. 55 Disadvantages .. 57 Size .. 57 Cost .. 57 Complexity .. 57 Design of MatrixIntercom Systems - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 61 Introduction .. 61 Back-to-Basics .. 61 RTS Matrix Intercom Systems .