TAPE REELS AND TAPE CARTRIDGES
There are two types of magnetic tape carriers: tape reels and tape cartridges. Both types can be used for either analog or digital recording. Tape cartridges are normally used only for digital recording.
Tape reels are used on magnetic recorders that use a manually loaded tape supply reel and a separate take-up reel. A reel's purpose is to protect the magnetic tape from damage and contamination. It can be made of plastic, metal, or glass. A reel has two parts, the hub and the flanges.
A tape reel is designed to hold magnetic tape on its hub without letting the magnetic tape touch the sides of the flanges. Contrary to popular belief, the flanges are not designed to guide the magnetic tape onto the tape reel.
Tape cartridges hold a spool of magnetic tape in the same way as tape reels, except that the inside of the cartridge contains both the supply reel and the take-up reel. Unlike tape reels which must be manually loaded into a recorder, when you insert a tape cartridge into a recorder, it's automatically loaded and ready to use. Figure 2-6 shows two typical tape cartridges.
Figure 2-6. - Typical tape cartridges.
TAPE ERASING AND DEGAUSSING
One advantage of magnetic tape is that you can erase what you've previously recorded, and record on the same tape again and again. The erasing is done by demagnetizing the magnetic tape. You demagnetize a magnetic tape by exposing it to a gradually decreasing ac (alternating current) magnetic field. There are two ways to do this: (1) with an erase head that's mounted on the magnetic recorder, or (2) with a separate tape degausser.
A magnetic recorder's erase head erases magnetic tape by saturating it with an ac signal that's higher in frequency than the frequency range of the recorder itself. This method of erasing a tape works well in some cases, but it's not the best way because:
It's slow; the tape must be run through the recorder to be erased. If the erase head is not completely demagnetized, it may not do a complete erasure. Some recorders do not have erase heads installed.
MAGNETIC TAPE DEGAUSSERS
By far, the best way to erase a magnetic tape is to use a separate magnetic tape degausser. There are two types of degaussers: automatic and manual.
Automatic Tape Degausser
Automatic degaussers erase magnetic tape by automatically moving the whole tape reel or cartridge slowly and steadily in and out of an intense ac magnetic field. This type of degausser erases a tape very well. Some automatic degaussers are made specifically for tape reels, and some are made for both tape reels and tape cartridges. Figure 2-7 shows a typical automatic degausser.
Figure 2-7. - Automatic tape degausser.
Manual Tape Degausser
Both manual and automatic tape degaussers use the same electronic principles for erasing magnetic tape. However, the manual version is much more portable. It's small, hand-held, and much less expensive. Figure 2-8 shows a typical manual degausser.
Figure 2-8. - Manual tape degausser.
To erase tapes with a manual degausser:
Q.28 What are two disadvantages of using a recorder's erase head to erase data recorded
on a magnetic tape?