ISDN interfaces (BRI-S, BRI-T and PRI) and CAS

Terminal interface BRI-S

The S user-network interface is a digital 4-wire interface used for connecting ISDN phones, Terminal Adapters and ISDN PC cards. This makes it possible to establish two independent call or data connections simultaneously. Up to 8 terminals can be operated on the BRI-S bus.

Table 1. Settings for BRI-S interface (internal type)
Parameter	Explanation
BRI-S protocol	ETSI: Choosing the protocol sets the Interface type to Internal after the settings are applied.
BRI-S bus length	Short: The BRI-S bus has a maximum length of 150 m or, if V-shaped, a maximum of 2 x 150 m. Up to 8 terminals are permitted. Long: The BRI-S bus has a maximum length of 1.000 m in the case of one terminal or a maximum of 500 m in the case of 4 terminals. In the case of 4 terminals the terminals must not be more than 20 m apart. Note: Always terminate the bus extremity with resistors (2 x 100 Ohm). More detailed information can be found in the relevant platform's System Manual
BRI-S MSN format	Terminal selection digit (TSD): A single digit number is used to address the terminals. Call number: The call number is used to address the terminals. This is the mode of operation normally used in the public ISDN network. Direct dialling number: The DDI is used to address the terminals. This is used for special applications (e.g. Unified Messaging Systems). If the DDI number is missing, the system attempts to transmit one of the following numbers, in the sequence shown below: number of the call distribution element, user group number, user number.
Remove exchange access prefix	Activate this check box if the exchange access prefix is to be deleted in the CLIP of an incoming call.

(Basic access) BRI-S external

The basic access BRI-S external is a terminal interface BRI-S configured as an external interface. It is suitable for connection to the private leased line network or for connection of a DSS1 terminal equipment capable of evaluating dialling-in numbers transmitted by the communication server (e.g. an external fax server).

Table 2. Settings for BRI-S interface (external type)
Parameter	Explanation
BRI-S protocol	BRI-S extern: Choosing the protocol sets the Interface type to External after the settings are applied.
Outgoing barred	An outgoing call cannot be made via this network interface.

Network interface BRI-T (basic access)

The basic access BRI-T has 2 user information channels and 1 data channel. It is suitable for connection to the public ISDN network (DSS1) or the private leased line network (QSIG/PSS1).

Table 3. Settings for BRI-T interface
Parameter	Explanation
Outgoing barred	An outgoing call cannot be made via this network interface.
TEI management	“TEI” stands for “Terminal Endpoint Identifier”. The TEI management parameter is used to specify the type of ISDN basic access: P-P (point-to-point): This is the usual connection type (default setting). With the aid of a direct dialling plan the users of the communication system can be reached directly using their DDI number. Note: No additional terminals may be connected at the BRI-T interface with point-to-point connection in parallel with the communication server. P-MP (point-to-multipoint): Some network providers allow the connection type with multiple subscriber numbers (MSN). Here a DDI number with all the digits of the MSN number has to be created for each MSN number.
Collision detection possibility	Status display
Collision detection	If terminals are connected in parallel on the BRI-T interface (point-to-point only), “Collision detection” has to be activated as the communication server and the terminal influence each other.
Layer 2 reactivation	In some countries BRI-T network interfaces are deactivated once a certain amount of time has elapsed without traffic, and are only reactivated when the communication server once again requests a connection. Layer 2 of the BRI-T network interface can be reactivated periodically every three minutes so that incoming calls are not rejected already at the local exchange after potential temporary interruptions in the U interface. For this, set the Layer 2 reactivation parameter to Special.
Layer 2 CMD / RESP

Network interface PRI (E1)(primary rate access)

The primary rate access has 30 user information channels and 1 data channel. It is suitable for connection to the public ISDN network (DSS1) or the private leased line network (QSIG/PSS1).

Only 30 user information channels of a primary rate interface can be divided into 4 B channel groups. This classification is carried out only if, for example, not all the B channels of the primary rate access are available. The B channel groups can be separately assigned to a trunk group.

Table 4. Settings for PRI interface
Parameter	Explanation
Trunk groups	Trunk group allocation
Hunt mode	Forward/Reverse/None: specifies the search direction inside the channel group
Start B channel	First B channel of this channel group
Last B channel	Stop B channel of this channel group
Layer 2 CMD / RESP

Network interface PRI (T1) (primary rate access)

This is the primary rate access for the public network in USA and Canada. It can be set for the protocols: 4ESS and 5EES (AT&T), DMS100 (Nortel), National ISDN 2 (Bellcore).

This type of primary rate access has 23 B channels and 1 D channel (23B+D).

It is supported only on the 1PRI-T1 cards of a Mitel 470 communication server.

CAS on the primary rate interface

CAS (channel-associated signalling) is a signalling protocol for PRI network interfaces that is used in certain countries (e.g. Brazil). This setting provides audio transmitters and audio receiver for transmitting the signalling information.

DSP resources (CAS senders/receivers) are required for CAS. With Mitel 470, DSP resources for 1 PRI interface are already available on each basic system (on the DSP chip on the call manager card with fixed function assignment). If more CAS senders/receivers are needed, they can be assigned on a configurable DSP chip. On a Mitel 430, the DSP resources for CAS senders/receivers must always be assigned on a configurable DSP chip.

If less than 30 B channels are available, you can split the CAS connection into several channel groups. Group unused channel groups together into an "unused" group

Table 5. Settings for CAS interface
Parameter	Explanation
Outgoing barred	Outgoing calls cannot be made via these network interfaces (does not apply to PRI interfaces).
Synchronisation member
Synch state
Collect call blocking signal	If the provider does not support the methods with the MFC/R2 signal for the recognition of collect calls (default value), the parameter must be set to double answer.
Hunt mode	Forward/Reverse/None: specifies the search direction inside the channel group
Start B channel	First B channel of this channel group
Last B channel	Stop B channel of this channel group