EDN Access--01.01.98 Fax saver cuts wear, tear, and power

-January 01, 1998

January 1, 1998

Fax saver cuts wear, tear, and power

Hugh Adams, Fort Walton Beach, FL

You can build the circuit in Figure 1 for less than $20 to cut wear and tear on your fax machine while saving power. If your fax machine has a dedicated phone line, the circuit intercepts the incoming ring signal and powers up the fax machine in time to receive the fax. It then turns off the fax machine after a predetermined time and awaits the next incoming fax. A relay in the line-cord circuit of the machine provides the turn-on and -off functions. If you build the fax saver in a small, plastic, outlet-type box, you can plug the fax machine into the box and wire the phone line in parallel with the machine's phone line.

The circuit incorporates protection against phone-line transients and draws its power from the normal 48V dc on the phone line; you thus need to exercise care in relay selection. Suitable relays are available at low cost from major distributors. The circuit function centers on a long-countdown device, IC1, whose overall delay depends on the external passive components. Q1 and Q2 require a high VCE rating to accommodate transients that can appear on the incoming phone line. (DI #2142)

Figure 1
Put your fax machine to sleep with this easy-to-build circuit that saves wear and tear as well as power.

| EDN Access | Feedback | Table of Contents |

Copyright c 1997 EDN Magazine, EDN Access. EDN is a registered trademark of Reed Properties Inc, used under license. EDN is published by Cahners Publishing Company, a unit of Reed Elsevier Inc.

Loading comments...

Write a Comment

To comment please Log In