Brooks RM 909 reviews Beats Per Minute BPM

The number of steady even pulses in music occurring in one minute and there fore defining the tempo of the song.

Fidelity
The recording or reproduction quality.

Brooks HI FI projectors Crossover Frequency
1) The frequency that is the outer limit of one of the bands of a crossover.
2) In the Lexicon 480L delay/reverberation effects unit, the frequency at which the bass frequency reverb time is in effect rather than the mid frequency reverb time.

Edit
A switch that does different things depending on the operational mode that the machine is in:
1) If a computer-controlled transport is in "Stop," pushing the "Edit" switch deactivates the computer-controlled tension system and allows the reels to be moved by hand to find the exact spot desired on the tape.
2) If the machine is in "Play", the "Edit" switch makes the take-up reel cease taking up the tape and it falls to the floor.
3) If the machine is in a fast-wind mode, the tape lifters are defeated so the tape is in contact with the reproduce head and the engineer can hear where the selections begin and end.

Brooks Hi Fi reviews DC
Abbreviation for direct current.

Bar
A term meaning the same thing as the term Measure (the grouping of a number of beats in music, most-often four beats).

AC
1) Abbreviation for alternating current.
2) An abbreviation of the term Alternating Current (electric current which flows back and forth in a circuit; all studio signals running through audio lines are AC).

Headroom
1) The level difference (in dB) between normal operating level and clipping level in an amplifier or audio device.
2) A similar level difference between normal tape operating level and the level where the distortion would be 3%.
3) The difference, in decibels, between the peak and RMS levels in program material.