HANDBOOK OF INTERCOM SYSTEMS ENGINEERING FIRST EDITION 38109-977 Rev. 4 The Fine Print The 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 law. Address copying inquires to: Bosch Communications Systems Telex Communications, Inc. Attn: Intercom Department 12000 Portland Ave S Burnsville, Minnesota 55337 USA Information contained in this work has been created or obtained by Telex Communications Inc. 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 assistance. TABLE OF CONTENTS Preface- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -3 About the Authors - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -5 Intercoms—An Overview - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -1 Introduction . .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-Line Intercom 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 . .8 A 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) . 16 (Present Day Systems and Manufacturers) . 16 (System Components and Their Function) . 17 (How Each System Works). 17 (Outstanding Features of Each System) . 18 i (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 . 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 . ..