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7.7.4. Simplex Speakerphone Configuration
Simplex Speakerphone (SSP) is a special case of speakerphone operation. Like speakerphone, it allows two-way
hands-free voice communication over a telephone line, but SSP allows communication in only one direction at a
time. The direction of voice transmission can be controlled automatically, based on the presence of local and
remote speech at the modem, or manually using a push-to-talk function. Simplex and full-duplex speakerphone
modes are mutually exclusive. Commonality in control registers between SSP and full duplex facilitates
programming across platforms.
SSP supports the Ademco Contact ID and SIA security protocols. It also supports DTMF generation and detection.
DTMF detection is enabled only VTR.
SSP supports Type II Caller ID. A DLE<R> event report is sent to the DTE when a SAS Call Waiting tone is
detected. If a CAS tone is detected, the modem mutes the Si3000 speaker while Caller ID Type II data are being
captured. It then reports Caller ID info to the DTE as a DLE-shielded complex event. This happens automatically,
without the need for an AT+VCIDR? command. Caller ID is disabled VRX.
Referring to Figure 31 on page 200, the microphone sample and speaker sample are taken before U19D and
U19C, respectively.
To mute the local talker, set SMUTE = 1 (U199 [1] = 1). To mute the remote talker, set MMUTE = 1 (U199 [3] = 1).
Configuring the modem to automatically switch between local talker and remote talker is as follows:
For the SSP auto-switch function, set SSP_FLAG to 1 (U199 [6] = 1) and SSP_PTT to 0 (U199 [7] = 0).
Set the speaker and microphone level thresholds, which determine whether remote speech or local speech is
active. The thresholds are defined in U1D6 and U1D7. Typical values for the speaker and microphone
thresholds are 0x400 and 0x400, respectively. These thresholds are not affected by the speaker and
microphone control gains UB5 and UB1.
Set the holding time, which is the time that the SSP holds the current mode after the signal level falls below the
threshold. Holding time prevents frequent mode switching between RX and TX. A typical value for holding time
is 0xC8 (200 ms).
For manual operation (push-to-talk):
Set SSP_FLAG to 1 (U199 [6] = 1) and SSP_PTT to 1 (U199 [7] = 1).
Use the SSP_LOCTALK bit (U199 [8]) to set the speech direction: U199 [8] = 1 for local talker; U199 [8] = 0 for
remote talker.
U1D8 is the break-through threshold for the speaker signal in SSP auto-switch mode. If the speaker signal is above
the threshold U1D8 and holds at least for the holding time, the direction is switched to remote talker, no matter how
strong the signal in the microphone is. To disable break-through, set the threshold to 7FFFh (AT:U1D8,7FFF).
U1D8 greater than U1D6: when the speaker signal is greater than or equal to U1D8, the microphone is muted
and speaker unmuted immediately, regardless of the microphone holding time. When the speaker signal is
greater than U1D6 but less than U1D8, the speaker signal goes through after the expiration of the microphone
holding time.
Table 150. Simplex Speakerphone U Registers
Register
Name
Description
Default
Value
U1D5
SSPHLDTIM
Extra time SSP stays in RX or TX mode to prevent frequent switch-
ing
0x0000
U1D6
SSPLTHRSH
Local talker threshold
0x0000
U1D7
SSPRTHRSH
Remote talker threshold
0x0000
U1D8
SSPBKTHRU
Break-through threshold for speaker in auto-switch mode.
Disable feature by setting this to 7FFFh.
0x7FFF
Содержание Si2404
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Страница 27: ...AN93 Rev 1 4 27 Figure 7 Parallel Interface Read Timing Figure 8 Parallel Interface Write Timing ...
Страница 200: ...AN93 200 Rev 1 4 Figure 31 TAM Handset and Speakerphone Voice Paths ...
Страница 201: ...AN93 Rev 1 4 201 Figure 32 Si3000 Codec Gain and Signal Selection Options ...
Страница 290: ...AN93 290 Rev 1 4 Figure 57 256 Band Spectral Display Figure 58 2048 Band Spectral Display ...
Страница 305: ...AN93 Rev 1 4 305 Figure 76 Parallel or SPI Port Interrupt Service Flowchart ...