Editing Cassette deck (section)

==== Advances in tape materials ====
New tape formulations were introduced. 
[[Chromium dioxide]] (referred to as CrO<sub>2</sub> or Type II) was the first tape designed for extended high-frequency response, but it required higher bias. Later, as the IEC Type II standard was defined, a different equalization settings was also mandated to reduce hiss, thus giving up some extension at the high end of the audio spectrum. 
Better-quality cassette recorders soon appeared with a switch for the tape type. 
Later decks incorporated coded holes in the shell to autodetect the tape type. 
Chromium dioxide tape was thought to cause increased wear on the heads, so TDK and Maxell adapted cobalt-doped ferric formulations to mimic CrO<sub>2</sub>. 
Sony briefly tried FerriChrome (Type III) which claimed to combine the best of both; some people, however, stated that the reverse was true because the Cr top layer seemed to wear off quickly, reducing this type to Fe in practice. Most recent decks produce the best response and dynamic headroom with metal tapes (IEC Type IV) which require still higher bias for recording, though they will play back correctly at the II setting since the equalization is the same.