A. GENERAL INFORMATION
A-5
BeFREE 20 – TECHNICAL OVERVIEW
AUDIO SECTION (INTERCOM)
♦
Loudspeakers (Left and Right)
two in parallel within the left output
two in parallel within the right output
type: dynamic
rated power: 3 W
output sound pressure level (SPL): 84 dB ± 3 dB @ 1 W @ 1 kHz @ 0.5 m distance
♦
Loudspeaker (Central)
type: dynamic
rated power: 10 W
output sound pressure level (SPL): 87 dB ± 3 dB @ 1 W @ 1 kHz @ 0.5 m distance
♦
Goose-neck Microphone
type: electret condenser, unidirectional
max input: 120 dB SPL
♦
Analogue Amplifiers
designed to meet wide-band IP telephony standards
frequency pass-band: (100 Hz - 8 kHz)
TYP
output power: 5 x 1 W (2 x 2 x 1 W + 1 x 1 W)
♦
USB Audio Codecs
model: Texas Instruments PCM 2900
C
(Codec A) & PCM 2902
C
(Codec B)
USB Interface: full-speed, USB 2.0 compliant, certified by USB-IF
resolution: 16-bit Delta-Sigma ADC and DAC
sampling rates (ADC): 8, 11.025, 16, 22.05, 32, 44.1, 48 kHz
sampling rates (DAC): 32, 44.1, 48 kHz
recommended data format:
16-bit
(rather than 8-bit),
stereo
(rather than mono)
MECHANICAL KEYS
♦
Push To Talk Key
(two key-switches in parallel)
model: Cherry MX
key travel: 3.6mm to 4.0mm total, (2
±
0.6) mm pretravel
actuating force: (60
±
20) cN
reliability (Mean Cycles To Failure): MCTF = 1 billion (10
9
) press/release cycles
(50 million is guaranteed minimum)
♦
Control Keys
model: Diptronic DTS
key travel (typical): 0.3mm
actuating force (typical): 255 cN
lifetime (minimal): 0.5 million operations
