Built-In Interfaces; Audio - HP 743 Service Handbook

Functional Description

Built-in Interfaces

Built-in Interfaces
The system board's built-in interfaces have ports on the front panel. Many of the ports are
micro-miniature connectors, requiring special conversion cables to interface with a
devices' standard connector.
The following sections provide more information on the function of each interface.

Audio

Model 743 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. Output is
provided by a small internal speaker and a stereo headphone mini-plug (8 Ohms imped-
ance). Input is provided by a stereo line-in and mono microphone mini-plugs.
A Digital Signal Processor (DSP) based option card is provided to enhance the audio sub-
system by providing phone and modem functions. Other special DSP applications can also
be down-loaded to this card.
The CODEC combines CD quality stereo A/D converters for microphone and line input
levels. 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 recording levels) and output attenuation.
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A / -inch. mini-jack is used for the speaker out connection. The other audio signals are on
8
a 9 pin micro D-sub connector. The output is capable of driving 8 Ohms; it can also be
used for higher impedance devices with little or no additional distortion. A line level
input can be driven by the headset output.
For information on programming for audio, refer to Using the Audio Developer's Kit
(B2355-90069) and the man page audio.
Table 2-5 lists the audio specifications, Figure 2-3 shows the audio connector, and Table 2-
6 shows the audio connector pinouts.
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