kotlas@ecsvax.UUCP (Carolyn Kotlas) (08/20/87)
We just got a new IBM Proprinter with a printer cable which has a small black box attached to the cable. This is a "ferrite filter" which, upon opening it up to examine the contents, appears to be a weak magnet (it isn't strong enough to pick up paperclips). Weak though it may be, can anyone tell us if this filter could damage floppy disk data? Thanks for any insight into this, Carolyn -- Carolyn Kotlas (kotlas@ecsvax) UNC-Educational Computing Service P. O. Box 12035 2 Davis Drive Research Triangle Park, NC 27709 State Courier #315 919/549-0671
feg@clyde.ATT.COM (Forrest Gehrke) (08/21/87)
In article <3732@ecsvax.UUCP>, kotlas@ecsvax.UUCP (Carolyn Kotlas) writes: > > We just got a new IBM Proprinter with a printer cable which has a small > black box attached to the cable. This is a "ferrite filter" which, upon > opening it up to examine the contents, appears to be a weak magnet (it > isn't strong enough to pick up paperclips). Weak though it may be, can > anyone tell us if this filter could damage floppy disk data? If this is indeed a ferrite filter, it probably is there to filter out any strong nearby radio frequency fields (which would mess up what the printer is supposed to print). Ferrites are not strongly magnetic and unless you insisted on rubbing the surface of a floppy against it, the data would remain intact. Nevertheless you would be advised not to place floppies on the box containing this filter, as you would also be advised generally not to allow floppies to lie on any magnetized surface. Floppies use a magnetic medium to record data in the form of localized magnetic fields. Changing these fields by bringing a magnetic field close to the surface of a floppy will damage this data. Forrest Gehrke
wheels@mks.UUCP (Gerry Wheeler) (08/21/87)
In article <3732@ecsvax.UUCP>, kotlas@ecsvax.UUCP (Carolyn Kotlas) writes: > > We just got a new IBM Proprinter with a printer cable which has a small > black box attached to the cable. This is a "ferrite filter" which, upon > opening it up to examine the contents, appears to be a weak magnet (it > isn't strong enough to pick up paperclips). Weak though it may be, can > anyone tell us if this filter could damage floppy disk data? > Thanks for any insight into this, The ferrite is not usually a magnet. It is just a hunk of metal that serves to add inductance to the cable, thus preventing high frequency noise from getting from one end to the other. If you really want to test it, though, just use a newly formatted disk, put some files on it, rub the ferrite against it, then see if you can read all the files. If it does mess up the disk, post a warning and reformat the disk. If it doesn't, then you're safe. -- ll // // ,'/~~\' Gerry Wheeler {decvax,ihnp4,seismo}!watmath!mks!wheels /ll/// //l' `\\\ Mortice Kern Systems Inc. (519) 884-2251 / l //_// ll\___/ 43 Bridgeport Rd. E., Waterloo, ON, Can. N2J 2J4 O_/
kotlas@ecsvax.UUCP (Carolyn Kotlas) (08/22/87)
> > > > We just got a new IBM Proprinter with a printer cable which has a small > > black box attached to the cable. This is a "ferrite filter" which, upon > > opening it up to examine the contents, appears to be a weak magnet (it > > isn't strong enough to pick up paperclips). Weak though it may be, can > > anyone tell us if this filter could damage floppy disk data? > Here's some more responses I received from my query. Thanks for all the information. --- You do not have to worry about the torroid filter on your printer cable. It is a non-magnetic powdered iron ferrite torroidal core that is used to prevent the cable from passing radio frequency or audio frequency currents, while still passing low audio frequency digital characters. These types of filters are common these days. They will have just a slight magnetic field around them when data is going by or if the printer cable has a voltage on it. Such magnetic fields are relatively small, and if the thing is even remotely shielded (as in some sort of a box), there should be no stray magnetic field at approximately 3 times the diameter from the core. The design of the torroidal core is such that essentially all of the magnetic field that might be induced in the core are retained essentially inside the core. You should be able to place a disk very close or even on the filter and have essentially zero effect. To check this out, copy some files to fill up a disk, place the disk on the filter for several weeks, then run a chkdsk on the disk to see if anything was messed up. Alternatively, make up two identical disks, placing one on the filter and another in a safe place. After several weeks, run a disk compare between the two disks. R. D. Keys -- rdkeys@ecsvax ___________ Yeah, we have these things too. I'm seeing them pop up all over, mostly on video cables (eg. Multisync). Question is -- do they really do much at all? (Or merely a prop to obtain FCC certification or something?) Thomas M. Hundt / BELLCORE Morristown NJ / hundt@bellcore.bellcore.com -- Carolyn Kotlas (kotlas@ecsvax) UNC-Educational Computing Service P. O. Box 12035 2 Davis Drive Research Triangle Park, NC 27709 State Courier #315 919/549-0671