Telex 38109-977 manual Introduction, Party-Line Systems

C H A P T E R

1

INTERCOMS—AN OVERVIEW

RALPH STRADER

Introduction

Intercom systems, by definition, may be comprised of many different types of intercoms and subsystems. The basic building blocks can be categorized into four basic types or elements: Party-Line Systems, Matrix Systems, Wireless Systems, and Accessories.

Party-Line Systems

Wired Party-Line systems are systems in which a number of participants are all involved in the same conversation. Think of the telephone extensions in your home, if each person in your family picks up a telephone in your home, you will all be able to hear each other. You can talk to one another simultaneously and the person “on the other end of the line” will be a full participant in one “public” conversation.

Depending on where in the world you are from, (presuming English language), you may also refer to this type of system as “PL” (for “party-line), “TW” or “Two-Wire” from the telephone systems, where on two wires, a full duplex conversation takes place, or “conference” denoting the type of activity taking place in the conversation.

Figure 1.1 Simple Party-Line System

Note, the physical configuration and implementation of that “PL” or “TW” does not necessarily need to be on two physical wires, in most cases it is not. The specific topologies will be addressed in the chapters that follow.

C h a p t e r 1 - I n t e r c o m s — A n O v e r v i e w 1