RC56D, RC336D, and RC144D Modem Device Sets Designer’s Guide
2-6
Conexant
1154
2.9.7 Sound Card Support Modes
Mute Handset; Route Sound Chips Output To Line. This mode mutes the local handset and routes the sound chip output
(such as music or messages during telephone hold) by switching the handset out of the telephone line path if necessary.
Record Conversation through Sound Chips. This mode allows recording of conversation through sound chips (valid after
the modem is offhook, e.g., from an ATA or ATD command).
Recording/Playback from Local Handset through Sound Chips. This mode routes the handset lines to the sound chips to
allow recording/playback of audio through the local handset.
2.10 SIMULTANEOUS AUDIO/VOICE AND DATA (AUDIOSPAN)
The modem can operate in AudioSpan Mode if the remote modem is also configured for AudioSpan Mode operation.
V.61 modulation supports 4800 bps data speed with audio, and a data-only speed of 4800 bps.
2.10.1 AudioSpan Mode Selection
AudioSpan Mode is selected with the -SMS=2 (AudioSpan Mode) or the -SMS=3 (Automatic DSVD/AudioSpan/Data Only
Mode Select) command. The local modem should be set to the AudioSpan Mode (-SMS=2) when sending, and to the
AudioSpan Mode (-SMS=2) or Automatic DSVD/AudioSpan/Data Only Mode Select (-SMS=3) when receiving.
2.10.2 AudioSpan Audio Interface
The AudioSpan audio interface defaults to the local handset connected to the modem and can be configured to interface
through the modem microphone and speaker pins to support use of a headset or a speakerphone.
2.10.3 Audio Quality Considerations
AudioSpan audio quality is dependent upon telephone line quality. Higher quality telephone lines provide better audio quality
than impaired telephone lines.
2.11 ON-BOARD DSVD MODE
On-Board DSVD operation is enabled by the -SMS =1 and the +FCLASS=0 commands.
In On-Board DSVD Mode, the RCDSVD SCP is connected to a MCU and to a handset or to a microphone/speaker
arrangement (e.g., in a speakerphone or a headset). The SCP converts analog speech input from a handset, microphone, or
headset to digital form, encodes the digital speech, and stores it in SCP interface memory for MCU access. The MCU reads
the data from SCP interface memory, multiplexes the encoded speech with other data and sends the combined data stream
to the MDP for modulation and transmission through telephone line interface circuitry over the telephone network to the
remote modem.
The received signal from the telephone line is demodulated by the local MDP and the data demultiplexed by the MCU into
data and encoded speech. The MCU then writes the demultiplexed encoded speech to the SCP interface memory. The SCP
decodes the encoded speech, converts it to analog form, and outputs it to a handset, speaker, or headset.
The MCU can switch between handset, half-duplex speakerphone, or headset use during a conversation.
The SCP performs voice encoding only after speech is detected to prevent encoding of background noise in order to
maximize data modem throughput during periods of voice silence.
2.11.1 DSVD Handset Mode
The modem supports DSVD handset operation when +VLS=0.
2.11.2 DSVD Headset Mode
The modem supports DSVD headset operation when +VSP=1.
2.11.3 DSVD Half-Duplex Speakerphone (HDSP) Mode
The modem supports DSVD HDSP operation when +VSP=1.
Summary of Contents for RC144D
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