Honeywell Galaxy Dimension Series Installer Manual page 202

56 - Communications (cont'd) Galaxy Dimension Installer Manual
2 = Point to Point
Only one device is allowed on the ISDN bus. In this configuration a TEI number must be programmed. The
default is 0. Since only one device is allowed the ISDN module will act differently when programmed to Point
to Point. The hardware ISDN snatch relay is always activated before the module starts a dialling sequence.
After all the alarms are transmitted the relay will be deactivated and the customer PABX, if connected, will be
connected to the ISDN network again. During the dialling sequence it is not possible to use the PABX for an
outside call. Upon an incoming call for the module, the relay will be activated directly switching the PABX off
the ISDN line, after which the ISDN module will seize the line. To ensure correct functionality of the PABX
and the ISDN module always connect the PABX to the ISDN out ports. The phone numbers that are avail-
able on a Point-to-Point line often only vary in the last 2 digits e.g.123401 ~ 123409. To handle incoming
calls from Remote Servicing one phone number need to programmed into the ISDN module. This specific
phone number cannot be used by the PABX because the ISDN module will seize the incoming call directly.
NOTE: X.25 in combination with a Point-to-Point ISDN line is not possible.
56.3.04 ISDN Snatch
In order to ensure maximum security the ISDN Module must be able to make a call in every circumstance.
The ISDN Module offers both hardware and software line seizure options.
1 = Hardware
The hardware snatch is performed using a relay. This relay can switch the other devices off when the ISDN
Module needs to communicate. In order to switch the other devices off it is important that these other devices
are connected to the ISDN out connection of the module. Some ISDN devices are not willing to release a B-
channel even when the network indicates that the B-channel must be released. When this is detected or a
tamper causes interference on the ISDN bus communication the relay will be activated.
A number of configurations are available for the hardware snatch function.
1 = Always Snatch
A hardware snatch is always attempted irrespective of the software snatch programming.
2 = Never Snatch
A hardware snatch is never attempted.
3 = Snatch if Fail
A hardware snatch is attempted if the software snatch fails or the software snatch is disabled.
2 = Software
The software in the ISDN module monitors every communication on the ISDN bus including those of other
devices. The software snatch enables the possibility to clear a B-channel when both are occupied at that time.
When both B-channels are occupied the ISDN module always clears the call that started first.
Certain ISDN devices will not release the B-channel when a software snatch is attempted. In this case, de-
pending on the programming of option 56.3.4.1 = Hardware, a hardware snatch can be attempted to ensure
a channel is made available to the ISDN Module. Software snatch can be enabled or disabled.
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