Telos Zephyr Xstream User Manual page 235

All calls, regardless of call types, will be answered automatically.
ISDN
Circuit Switch Data calls (i.e. callers from a Zephyr Xstream when the Call Type is
set to "Zephyr") will be answered automatically. Circuit Switched Voice (i.e.
POTS/G.711) calls are treated as if "none" was selected.
Phone
Circuit Switch Voice calls (i.e. callers from an Xport on a POTS line, a regular
telephone, or a Zephyr Xstream when the Call Type is set to "Phone") will be
answered automatically. Circuit Switched Data calls are treated as if "none" was
selected.
Interface
The Interface selection will activate one of the following ports of the Zephyr
Xstream
ISDN/ISDN Modem
Either of these selections will enable the Zephyr Xstream's built‐in ISDN
interface, if present. The ISDN Modem selection loads the code required to talk
to the Zephyr Xport connected to a POTS (analog) line. When call is placed in
Phone Mode (in the DIAL menu), the Interface setting will change between ISDN
to ISDN Modem automatically. This will also occur when an incoming "voice"
call is answered, and can be ignored by the user; if an ISDN mode call is
subsequently made, or received, the unit will switch back to ISDN interface
automatically.
A note regarding Mode detection and Interface switching of incoming calls:
The ISDN network will signal if a call is "voice" or "data" call. Since modems use
POTS technology, calls from Xport are considered "voice" calls. In the case of a
"data" call, no other information is needed; the Xstream will switch from the
ISDN Modem Interface to ISDN, if necessary, and answer the call.
If the network indicates an incoming call is a "voice" call, the Xstream must
determine if this is a call from a telephone, or from the modem of an Xport.
Therefore, the Xstream switches the Interface selection from the ISDN to ISDN
Modem, if necessary, answers the call, and then listens for a modem carrier
tone. If no modem tone is detected, the unit un‐mutes the audio and the call is
considered a "Phone" Mode call. If a modem tone is detected, the Xstream's
modem will begin negotiating with the Xport.
Therefore, all incoming "voice" calls have a short delay before audio is heard.
V.35 Split
This selection will enable the Xstream's built‐in V.35/X.21 interface, if present.
USER'S MANUAL
Section 11: THE WORKS – Detailed Menu Reference 223