Technical data

1-20
General Information
Model 743 and Model 744 VME Board Computers
The sections that follow explain the functions of the interfaces.
Audio Model 743 and Model 744 Board Computers provide compact disc-quality audio
input and output, in stereo, with a 16-bit coder-decoder (CODEC) over a frequency range of
25-20,000 Hz. A stereo headphone mini-plug (8 ohms impedance) provides output. The ste-
reo line-in and mono microphone mini-plugs provide input with the HP A4302A Audio
Cable.
The CODEC combines CD quality stereo A/D converters for microphone and line input lev-
els. D/A converters for driving headset and line outputs are used. The input sampling rate and
format are programmable, as are the input gain control (used for software control of record-
ing levels) and output attenuation.
A
1
/
8
-inch mini-jack is used for the speaker out connection. The other audio signals are on a
9-pin micro D-sub connector. The output is capable of driving a minimum of 8 ohms. It can
also be used for higher impedance devices with little or no additional distortion.
A voice-quality audio output may be used.
For information on programming for audio, refer to Using the Audio Developer’s Kit (B2355-
90069) and the man page audio.
Table 1-14 lists the Model 743 and Model 744 audio specifications.
NOTE: Audio CD ROMs cannot output to the audio out connector.
Table 1-14 Model 743 and Model 744 Audio Specifications
Function Range
Headphone maximum
output level
2.75 V pp at 50 ohms
Input sensitivity Line in, 2.0 V pp at 47 K ohms microphone, 22 mV
at 1 K ohm
Programmable input gain 0 to 22.5 dB in 1.5 dB steps
Programmable output
attenuation
0 to 96 dB in 1.5 dB steps
Programmable rates 8, 11.025, 16, 22.05, 32, 44.1, 48 KHz
Signal to noise ratio Headphone, 61 dB
Line in, 61 dB
Microphone, 57 dB