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CPS - Article
Optimizing SOHO Telephone Lines with Call Waiting

CWS/TSS Picture In the past most SOHO installations utilized the common Voice/Fax/Modem sharing switches to get more use out of a phone line. The switches would simply recognize the inbound call as being for the fax, modem, or voice and switch it to the appropriate port where that device was connected.

However, most of the newer fax machines oriented toward SOHOs also have jacks for voice sets and answering machines. They identify inbound calls as being a fax (CNG tone) or a voice call... But what about the modem?

When you think about it, in today's world most modems are used for outbound access to the Internet or e-mail. So the reason for inbound modem recognition has all but disappeared. Also in many cases this increased outbound access requirement has also dictated the installation of a second line. However, after you graduated to multiple lines, the options for sharing multiple lines is drastically diminished.

You could then use all of your phone lines for outbound access

Perhaps a better idea in today's world would be to use call waiting and install a Call Waiting Switch on each line. You could then use all of your phone lines for outbound access (voice or data) without missing any inbound calls. The switch would interrupt a modem session anytime an inbound call was detected and automatically switch it to the fax machine or to your phone system allowing it to ring normally.

This is a slightly less expensive approach, from a hardware stand point, but the real savings is realized through the increased utilization of your phone lines. It can be used on single lines or multiple lines.

Look at the Call Waiting Comments to see why you need a Call Waiting Product.

Adding Modem Sharing
The sharing concept can be dramatically enhanced by adding a more modern day Telephone Sharing Switch (TSS) to the mix. It allows many more modems to contend for any available telephone line while eliminating interference from others that may also bid for a line. However, the "Phone Port" on the Call Waiting Switch would always have priority to make outbound fax or modem calls. This also allows the use of 56KB modems since the modems by-pass the phone system that may present a 9600 - 19.2KB restriction.

The following diagrams show how the hardware fits together and provides a general idea as to the cost. The pay out should be well under six months in telephone line savings.

Single Lines

Old vs. New Method Application Diagram


Adding a Modem Line Sharing Switch

Combination Application Diagram


Multiple Lines

Combination Application Diagram


Further information on any of these products is available from Computer Peripheral Systems, Inc. 1-800-888-0051 http://www.cpscom.com/share.htm.

NOTE: To determine the Telephone Line Cost Savings related to these products, use the Cost Comparison Calculator.


Computer Peripheral Systems, Inc.
5096 Bristol Industrial Way, Suite B
Buford, GA 30518
8:30 AM - 5:30 PM EST
Technical Support
(770) 945-0643
8:30 AM - 5:30 PM EST
(770) 945-9342

© Copyright 1996-2003  Computer Peripheral Systems, Inc.
This file last modified March 10, 1999