The Early Days of the Business Phone System Explained

The Early Days of the Business Phone System Explained

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This is chapter 2 of a multiple chapter learning exercise for those looking to buy a phone system for their business.

If you want to read chapter 1, you can find that here:  The Basics of Buying a Phone System for Your Business: A Phone System Buyer’s Guide

The Early Days of the Business Phone System

early days of the business phone systemWe’re going to take you back.  WAY BACK to the early days of the business phone system. Well, maybe not to the age of the dinosaur, but, close 🙂

What you see pictured is called a switchboard (also called a manual exchange). This was a device used to connect a group of telephones manually to one another or to an outside connection, within and between telephone exchanges or private branch exchanges (PBXs). The user was typically known as an operator. Public manual exchanges disappeared during the last half of the twentieth century, leaving a few PBXs working in offices and hotels as manual branch exchanges.


The switchboard is usually designed to enable the operator to sit in front of it. It has a high back panel which consists of rows of female jacks, each jack designated and wired as a local extension of the switchboard (which serves an individual subscriber) or as an incoming or outgoing trunk line. The jack is also associated with a lamp.

On the table or desk area in front of the operator are columns of keys, lamps and cords. Each column consists of a front key and a rear key, a front lamp and a rear lamp, followed by a front cord and a rear cord, making together a cord circuit.

The front key is the “talk” key allowing the operator to speak with that particular cord pair. The rear key on older “manual” boards and PBXs is used to physically ring a telephone, and on the newer boards, the back key is used to collect (retrieve) money from coin telephones.

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Each of the keys has three positions: back, normal, and forward. When a key is in the normal position, an electrical talk path connects the front and rear cords. A key in the forward position (front key) connects the operator to the cord pair, and a key in the back position sends a ring signal out on the cord (on older manual exchanges). Each cord has a three-wire TRS connector: tip and ring for testing, ringing, and voice; and a sleeve wire for busy signals.

When a call is received, a jack lamp lights up on the back panel and the operator responds by placing the rear cord into the jack and throwing the front key forward. The operator now converses with the caller and finds out to where the caller would like to be connected. If it is another extension, the operator places the front cord in the associated jack and pulls the front key backwards to ring the called party. After connecting, the operator leaves both cords “up” with the keys in the normal position and the parties can converse.

History of the First Phones

The History of the TelephoneThe early days of the business phone system started with the first telephones in the 1870s that were rented in pairs which could only talk to each other, but the example of a central exchange was soon found to be even more advantageous. Small towns typically had the operator’s switchboard installed in the operator’s home so that they could answer calls on a twenty-four-hour basis. In 1894, New England Telephone and Telegraph installed the first battery-operated switchboard on January 9 in Lexington, Massachusetts.

Early switchboards in large cities usually were mounted floor to ceiling in order to allow the operators to reach all the lines in the exchange. The operators were boys who would scoot up a ladder to connect to the higher jacks. Late in the 1890s, this measure failed to keep up with the increasing number of lines, and the Divided Multiple Switchboard was devised for operators to work together, with a team on the “A board” and another on the “B.” These operators were almost always women until the mid-1960s when men were once again hired. Early “cord” switchboards were often referred to as “cordboards” by telephone company personnel. Conversion to Panel switch and other automated operations in big cities first eliminated the “B” operator and then, years later, the “A”.

History of the telephone - ppt video online download

Telephone Exchanges

As telephone exchanges converted to automatic, or direct dial, service, switchboards remained in use for specialized purposes. Before the advent of direct-dialed long-distance calls, a subscriber would need to contact the long-distance operator in order to place a call. In large cities, there was often a special number, such as 1-1-2, which would ring the long-distance operator directly. In other cities, the subscriber would ask the local operator to ring the long-distance operator.

When calling long distance, the customer often wouldn’t have the phone number available, so would simply ask for the name and city of the person desired. The long-distance operator would plug into the trunk for the distant city, and the inward operator in the distant city would answer, obtain the number from their local information operator, and make the call.

Later, with the advent of multi-frequency operator dialing, the operator would plug into a trunk line and dial the area code and operator code for the information operator in the distant city. If the customer knew the number, and the point was direct-dialable, the operator could dial the call. If the distant city didn’t have dialable numbers, the operator would dial the code for the inward operator, and ask her to ring the number.What is a Telephone Operator? - Quora

After most phone subscribers had direct long-distance dialing, one type of operator served both the local and long-distance functions. A customer might call to request help getting through on a number that didn’t ring, or might be out of order, for instance. If the number was in a distant city, the operator would call the inward operator in the destination city, and ask her to try the number, or to test a line to see if it were busy or out of order. Cordboards for these purposes were replaced in the 1970s by TSPS and similar systems.

As the Central Office market changed, and grew, so the corporate market. The two technologies continued in step with one another. At the CO level, the operators handled calls and patched the callers though. They also did the same at the corporate level. The cordboard operator connected the call. The switching technology at the CO level, or Branch Exchange, improved to the point where the operator became redundant. The technology dealt with that facility of handling and patching the call through.

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Then, in the early 1970s the PBX came to the market. PBX, known as Private Branch Exchange, handled the switching that the company operator formerly handled. Hence the term ‘Private’ in the term Branch Exchange – private implying private corporate phone system. The PBX has traditionally been known as a TDM, or circuit-switched system, and has dominated the market for business telephone use.

From the early days of the business phone system to the phone system market today, TDM market is gradually transitioning toward Voice over IP – the next generation of telephone systems in the market.

This was chapter 2 of the series: How to Buy a Phone System for Your Business.

Let us move ahead to Chapter 3: What is Voice Over IP