and/or receive a busy signal to indicate that she/he should redial in these instances.
You can establish one of three types of priority which will determine how competing users
at the LSS are given access to the line. This is determined by a programming command,
as described in Chapter 4. The priority modes are:
If Total Priority Mode is enabled, Port 1 (normally a telephone) is given immediate
access to the line whenever the phone goes off-hook. If another port is using the line (for
example, data transfer is taking place), the modem is halted and the line made free for
the telephone user. Port 2 also has priority access over Ports 3 and 4, but not over Port 1;
Port 3 has priority access over Port 4, but not over Ports 1 and 2.
If Emergency Priority Mode is enabled, a Port 1 user is given priority when one of the
programmed emergency numbers is dialed. The LSS can be programmed to allow up to
ten 16-digit numbers. An Access Code can also be programmed to provide emergency
line access to allow any number to be dialed.
In this mode, Port 2 has total priority over Ports 3 and 4. This arrangement allows
time-sensitive credit card verification calls on equipment connected to Port 2 to take
priority over other calls.
Caution: If the LSS is receiving an incoming fax when you go off-hook in either Total
Priority Mode or Emergency Priority Mode, the LSS will be unable to obtain network dial
tone until the sending fax disconnects or the PSTN times out (usually within 10-15
seconds).
If No Priority Mode is enabled, no port can access the line when another port is using it.
Calling Party Supervision
The U.S. telephone network typically uses Calling Party Supervision. This means that
even though the called party hangs up, they may be reconnected to the calling party
when their phone is taken off-hook again. The calling party must hang up in order for the
called party to be fully disconnected and initiate a new call. The telephone network will
time out and automatically disconnect the call within 5 - 20 seconds, depending on
network design. This will allow the called party to get dial tone when they go off-hook
again.
To circumvent this problem, when the LSS senses a priority interrupt it immediately
signals the Polling Controller to disconnect the original polling call. Standalone users will
not have the benefit of the handshake and disconnect. If priority access to dial tone is
important, it is recommended that a Polling Controller be used. (See ordering information
in Appendix 2.) This procedure ensures that the user initiating the priority will have
access to network dial tone to complete the priority call. If for any reason the interrupted
call cannot be properly terminated within approximately 5 seconds, a line busy tone is
returned to the priority caller. The caller should then hang up for a few seconds before
trying the call again.
Outgoing Calls from the LSS
The LSS allows DTMF and rotary dialing on outgoing calls.
Telephone Calls—Modem or Other Device Idle
When the LSS is idle, local telephones are connected to a local battery feed. When a
phone goes off-hook, it is switched to the central office line to obtain dial tone. When the
phone goes on-hook, the line is switched back to a local battery feed.
Line Sharing Switch
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