the LSS connects Port 1 to the incoming call, and monitors for a DTMF transfer code
from the host site Polling Controller. If a DTMF transfer code is received, the LSS will split
the line. What happens next depends on which priority interrupt mode has been
programmed.
If the LSS is programmed for No Priority, the call will be routed to the appropriate port,
and Port 1 will receive busy tone.
If in Total Priority Mode, the LSS will perform a disconnect sequence as described
previously, and then connect the central office line to Port 1.
If in Emergency Priority Mode, the LSS will provide dial tone to Port 1, and the user
must dial one of the programmed emergency numbers to gain access to the central office
line. The LSS will not route the incoming call to the port selected by the transfer code until
either the caller is denied access due to dialing an invalid number, or 5 seconds after the
last digit dialed. This design will prevent any modem carrier from interfering with a
disconnect sequence if the caller dials a valid emergency number. If a valid emergency
number is dialed, the LSS will perform a disconnect sequence immediately.
If off-hook is detected on a port other than Port 1, before an incoming call rings the LSS,
the incoming call is connected to the port. If the LSS has detected ringing, or has already
answered the incoming call, and any port other than Port 1 goes off-hook, the LSS will
keep the talk path split for 4 seconds while it monitors for CNG tone or a DTMF string
from the Polling site. If CNG or the expected DTMF transfer code is received, the call is
handled as described previously in the “Outgoing Calls from the LSS” section. If a DTMF
transfer code is not received, the call is routed to Port 1, and the off-hook port will be left
connected to the local battery feed. No tones will be sent to the port.
Off-hook Timeout at the LSS
Occasionally, a need to set a maximum off-hook time is required. The LSS allows either
no limit or a programmable maximum time of up to 255 minutes per port. After an off-hook
timeout timer expires, the device connected to the port will be sent a forced disconnect
(COD) and the C.O. line will be placed on-hook. This off-hook timeout should be set to
encompass the expected duration of any polling or other call.
Privacy Timeout
When Privacy Timeout is enabled, any port remaining off-hook without dialing or
disconnecting properly, the LSS will connect the device to local battery feed and place the
incoming central office line on-hook to enable other ports to receive calls. This lockout of
an offending port occurs after first detecting
at least five seconds of Central Office dial
tone or two cycles of either busy or reorder tone during the first 15 seconds of off-hook,
and no DTMF digits and 5 or fewer rotary breaks dialed in 60 seconds.
If dial tone, busy, or reorder were not detected, or dialing was detected, the LSS will
monitor for either a hook-flash or forced disconnect. If a hook-flash or forced disconnect is
then detected, the LSS will re-start the privacy timeout period. No tones are sent to the
off-hook phone. Incoming calls to other ports (transfer code received from the Polling
Controller) are routed appropriately; calls to the off-hook privacy phone are given busy
tone.
If the port is returned to on-hook and then goes off-hook later, it will receive Central Office
dial tone per normal operation.
A number of operating parameters in the LSS can be adjusted by the customer. The
programming options are listed in Table 2. The LSS is programmed using a DTMF
Line Sharing Switch
Page 24