ZyXEL Communications 2864 - Manual (Page 179)

16–3
In ZyXEL voice mode, three states exist that roughly correspond to the flow direction of
the digitized voice data; the Voice Command State (no data transfer other than event re-
ports), the Voice Transmission State (digitized voice data transfer from the DTE to the
DCE), and the Voice Receival State (digitized voice data transfer from the DCE to the
DTE). Note that the voice data DTE/DCE transfer is half-duplex.
The DCE may issue event detection reports at any time, regardless of the DCE
state. These reports may be tone or cadence events in nature (such as calling tone
detection), or they may be a result of external switching functions of Telco line ac-
tivities (Ring), or they may be a combination (Caller ID). ZyXEL provides the
Service Level C Event Detection Capabilities of IS-101 as follows :
Voice Command State
The DCE is in the Voice Command State and ready to accept commands when the
DCE is operating in voice mode and is not communicating with a remote station,
nor with any local devices which are capable of translating analog signals to voice
(e.g., speaker) or translating voice to analog signals (e.g., microphone). The DCE
considers data transfers from the DTE to be commands, and returns responses back
to the DTE after completing the processing of the commands. While accepting or
processing commands, the DCE also monitors the line which connects the DCE to
the remote station or to the local device to detect events, which the DCE later re-
ports to the DTE pertaining to signals carried over the line, such as tones, and per-
taining to PSTN generated control and notification signals, such as ringing.
The Voice Command State provides several DTE options. The modem may wait
for an unspecified time after playing a welcome message, or switch to other modes
as part of a DTE call discrimination algorithm.
Event Description DCE Voice State
RING Command
Ringback Command
Fax or Data Answer (e.g., 2100Hz) Command
BUSY Receive, and Command
DIALTONE Receive, and Command
DTMF Received Receive, Transmit, and Command
Fax Calling Tone Receive, Transmit, and Command
Presumed Hang-up (SILENCE) Time-out Receive
Presumed End of Message (QUIET) Receive
Time-out
Mandatory Receive Buffer Overrun
Receive
Mandatory Transmission Buffer Underrun Transmit