10.1
Telecom standard
(1) The preferred method of connection to the Telecom network is now 2-wire and all new devices should be compatible with this arrangement.
* This is in line with most international standards.
(2) The previous Telecom standard was a 3-wire parallel connection arrangement, which included provision of a "ringer" capacitor, a surge suppressor and an "out-of-service" resistor in the network termination (Master Socket).
* Further information is given in Specification TNA 102, Section 9.
(3) Although 2-wire connection is preferred, the 3-wire method is still acceptable and both are described in this Section (see Fig. 10-1).
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10.2
Connection methods
(1) The primary method of connection of terminal equipment is via a plug to
BS 6312:1985, with the latch adjacent to plug pin 6. The plug mates with a standard Telecom socket which terminates the customer's premises wiring. This arrangement applies to both 2-wire and 3-wire connection (see also TNA 102, clause 9.3).
* The plug to BS 6312:1985 is commonly known as a "BT" plug. (2) (a) The socket/plug pin numbering is as follows:-
| Pin 1 | not used |
| Pin 2 | A-wire |
| Pin 3 | earth (when provided) |
| Pin 4 | ringer-wire (3-wire only) |
| Pin 5 | B-wire |
| Pin 6 | not used |
* The standard method of terminating the D-Section cordage automatically results in reversals occurring between the pin numbers of the plugs at each end of a telephone cord. For this reason suppliers shall take special care to ensure that the correct pin allocation is complied with when using 3-wire connections.
* It should be noted that the present terminating hardware used by Telecom in customer premises wiring introduces another numbering reversal between the socket pin numbers and the wiring terminal numbers (see TNA 102, clause 9.3(2)). Suppliers should be aware of this potential source of confusion.
(b) The 'A' & 'B' wires referred to (socket pins 2 & 5) are the two wires of the line to the Telecom local exchange and they form the basis of the 2-wire connection method. The 'ringer' wire is only used for 3-wire connection.
* The reference to 'A' & 'B' wires is used for convenience. They do not necessarily relate to any particular polarity since there is a high risk of line reversals occurring (see also clause 6.2(3)).
* Telecom is changing its standard premises wiring practice from the original '3-wire system' to a '2-wire' arrangement. The BT socket is being retained. These changes will only apply to new installations or rewiring situations and will, in any case, accommodate existing 3-wire connected CPE.
(3) An acceptable alternative plug and socket arrangement for 2-wire connection in business premises is the 8-way modular connector specified in IEC 603-7, and also in EIA/TIA-568 and EIA/TIA-570. The preferred pin-out designation is T568A, using pins 4 & 5 as shown in Technical Document TNA 102, Fig. 7.
* This modular connector is also specified in AS/NZS 3080:1996 and ISO/IEC 11801:1995.
* This 8-way plug and socket is commonly known as "RJ45" in New Zealand. However, this is not strictly the correct designation.
(4) Either BT plugs or 8-way modular plugs may be fitted on 2-wire connected CPE without the need for separate Telepermits. However, where the 8-way plug is fitted, this should be clearly shown on product packaging.
(5) Devices fitted with plugs of types other than those described above will be considered for the grant of a Telepermit in the following circumstances:-
(a) If a device is offered for sale complete with an adapter unit which provides a means of compliance with this Section.
(b) If a device is regarded as an integral part of another item of equipment. In this case the device may be connected to its 'parent' equipment by means of a non-standard plug and socket.
* An example of this is a facsimile machine with an integral one-piece telephone. Any Telepermit granted for such telephones will be as part of the facsimile machine, not as a "stand-alone" telephone instrument.
* A further example is a device connected to a PABX or KTS by means of a proprietary interface. Similarly, such a device will be treated as part of the PABX or KTS.
(c) Devices categorised as PABX's or key telephone systems which are designed to be hard wired to PSTN lines via a distribution terminal.
(6) All types of plugs or circumstances not covered by sub-clauses (1) to (5) above shall be regarded as unacceptable for Telepermit purposes.
* This exclusion applies also to the commonly known 'RJ11' or 'RJ12' miniature 4 way or 6 way version plug which will physically mate with an RJ45 socket. This combination is not considered satisfactory as the plug is insecure when in position and the plug moulding may overstress the outer springs of the socket.
10.3
Two-wire connection
The standard (preferred) method used for connection of customer equipment to the Telecom network is 2-wire (see Fig. 10-1(a)).
10.4
3-wire connection
(1) The previous Telecom standard arrangement for the connection of devices consists of a 3-wire configuration. The third wire is derived via a 1.8 µF capacitor and 470 kohm resistor mounted in the Master Socket and is known as the 'ringer' wire (see Fig. 10-1).
* The 3-wire connection arrangement is also described in Specification TNA 102, Section 9.
(2) Products using the 3-wire connection method are still acceptable for Telepermit purposes. However, there is no guarantee that this will always be the case.
NOTE: Both 2-wire & 3-wire CPE may be connected to either 2-wire or 3-wire jackpoints.
FIG. 10-1 2-WIRE & 3-WIRE CONNECTION ARRANGEMENTS
10.5
Earth connections
(See clause 2.8.4)
10.6
Modification of 3-wire devices for 2-wire operation
(1) There are many 3-wire telephones currently Telepermitted and installed in customer premises and there is at present no mandatory requirement for these to be modified.
(2) It is permissible for a supplier to choose to modify an existing 3-wire model of telephone for 2-wire operation. In such cases Access Standards shall be advised of details of the modification to ensure that the 'ringer' wire has been disconnected and that there has been no impact on product compliance. This applies even if the basic functional design is retained. Usually it will necessitate a retest and an application for the grant of a separate Telepermit for the 2-wire version.
* Conversion from 3-wire to 2-wire will almost certainly change the electro-acoustic performance and also may influence the line impedance.
* Reference clause 12.3
10.7
Series connected devices
10.7.1
(a) Connection shall only be implemented by means of a Telepermitted "Line Break-in Arrangement" (LBA) which provides the facility of isolating and bypassing the line grabbing device if required for any reason (see Fig. 10-4 for a typical LBA connection arrangement).
Line grabbing connections
(1) Some series connected devices incorporate a line grabbing function whereby all other equipment normally connected is isolated from the line. It is necessary to connect such equipment on the network side of all installed sockets and the following connection arrangements shall apply:-
* This ensures that whenever the line grabbing equipment is unplugged, the line is switched to the other sockets installed in the premises and normal calls can proceed.
* Fig. 10-4 shows use of a Type 2 Distinctive Alert decoder with an LBA. The Type 2 decoder is not strictly a line grabbing device but the method of connection is identical.
(b) Detailed instructions shall be given on the correct method of installing the equipment, and either:-
(i) These instructions shall nominate the actual hardware to be used, or,
(ii) the necessary hardware shall be supplied with the equipment
concerned.
(c) The equipment connection shall be such that it ensures connection of other socket terminations across the line in the idle condition.
* A typical example of such equipment is an alarm system designed to make calls in an emergency.
10.7.2
Handover
(1) A device may plug into a Telecom socket and provide its own extension socket. Another item of equipment plugged into that socket (usually a telephone) is used to establish a call. Once the call has been established, the equipment (usually under manual control) will then "grab" the Telecom line from the secondary device and continue with the same call.
(2) During a handover process any d.c. break shall be no greater than 9 ms.
(3) One of the following alternatives shall apply:-
(a) The appropriate requirements for 3-wire connection as detailed in clauses 10.2 and 10.4 of this Specification shall be complied with, or,
(b) If a 2-wire socket to clause 10.3 is used, the User Manual shall contain a warning to the effect that not all telephones will respond to incoming ringing when connected to the extension socket.
* A common example of this arrangement is a dedicated telephone connected to the extension socket of a modem or facsimile machine, preferably with no other equipment connected to the same line.
* Where any Telepermitted device may be associated with the port, that port shall support both 2-wire and 3-wire connected devices as required by clause 7.7.2(3).
10.7.3
Distinctive Alert decoders
(1) Type 2 Distinctive Alert decoders (ref. clauses 7.1 and 11.3) may be connected in the following ways:-
(a) Mode A (see Figs. 10-2(a), 10-2(b) & 10-2(c)) - These arrangements all consist of plug connections on the network side, with socket outlet(s) on the CPE side, into which other items may be directly connected. Fig. 10-2(a) shows connections for a multiple outlet decoder and Figs 10-2(b) and 10-2(c) show two examples of single output decoders.
* Mode A is the preferred option as it does not create potential maintenance problems by interfering with the fixed wiring.
FIG. 10-2(a) MODE A CONNECTION OF TYPE 2 DECODER (MULTIPLE OUTPUT DECODER)
FIG. 10-2(b) MODE A CONNECTION OF TYPE 2 DECODERS (SINGLE OULET DECODERS)
FIG. 10-2(c) MODE A CONNECTION WITH MIXED TYPE 1 AND TYPE 2 DECODERS * An example of use of a single outlet decoder is to prevent a bedside phone from ringing for an incoming fax call.
(b) Mode B (Fig. 10-3) - This arrangement consists of a plug connection on the network side and, on the terminal side, socket outlets with one or more connected to secondary fixed wiring.
(c) Mode C (Fig. 10-4) - This arrangement is similar to that for line grabbing equipment and provides a permanent connection to the fixed wiring on the network side, with one or more of the terminal side outlets connected to the premises fixed wiring.
(2) Mode C connections shall only be implemented by means of a Telepermitted "Line Break in Arrangement" (LBA) which provides the facility of isolating and bypassing the decoder in the event of it becoming faulty.
* Details of LBA requirements are given in Specification PTC 203. Fig. 10-4 indicates a direct (hard-wired) connection of the decoder to the LBA, however, consideration may be given for a plug and socket connection on the LBA.
(3) The user manuals accompanying all Type 2 decoders shall contain the following warning:-
" This [equipment/decoder] must not be connected to the fixed wiring
unless the connection is via a Telepermitted Line Break-in Arrangement.
Any non-Telepermitted connection methods will void the Telecom wiring maintenance agreement"
FIG. 10-3 MODE B CONNECTION OF TYPE 2 DECODER (MULTIPLE OUTPUT)
FIG. 10-4 MODE C CONNECTION OF TYPE 2 DECODER (MULTIPLE OUTPUT)
10.7.4
Fault clearance
(1) There are significant fault clearance considerations for series connected devices which impact on the premises wiring, which is to be maintained by Telecom. Mandatory requirements are detailed in the following sub-clauses. Two types of installation directly concerned are as follows:-
(a) Any installation with a device requiring secondary fixed wiring on the terminal side of the device.
* Typical examples are Type 2 PABX's, KTS and Type 2 Distinctive Alert decoders (Mode B connection). Larger Type 1 PABX's are regarded as a separate category and are covered by the PABX Specifications PTC 107, 108, 109 and 207.
(b) Any installation requiring an LBA.
* Typical examples are those with line grabbing facilities (alarm security systems, etc.) and Type 2 Distinctive Alert decoders (Mode C connection).
(2) Secondary fixed wiring (see Fig. 10-3)
"In the event of any problem with this device, it is to be disconnected, and
a CPE item connected to one of its terminal ports may be connected directly in its place. The user should then arrange for the product to be repaired. Should the matter be reported to Telecom as a wiring fault, and the fault be proven to be due to this product, a call-out charge will be incurred."
(3) LBA installations (see Fig. 10-4)
On installations which require a Telepermitted LBA, the customer will need to be aware of the necessary procedure in the event of a fault affecting the series connected device. The LBA provides a by-pass switch which allows the customer to manually by-pass the series connected device for servicing. Such wiring arrangements shall be covered in the User Manual for the series connected device concerned by an entry to the effect that:-
"In the event of any problem with this device, the by-pass switch should be operated. The user is to then arrange with the supplier of the device to make the necessary repairs.
Should the matter be reported to Telecom as a wiring fault and the fault is proven to this device, a call-out charge will be incurred.
Some devices are designed for installations where there is a possibility of secondary fixed wiring arrangements on the terminal outlet side. In such cases, the customer will need to be aware of the necessary procedure in the event of a fault affecting the series connected device. These devices shall have an entry in the User Manual as follows:-
* It is recommended that a fault alarm indication be provided where practicable.
* Note that as some devices switch through to one of their output ports under power failure conditions, service restoration may be temporarily achieved by switching off power to that device.
10.8
Connection method for externally mounted devices
(1) Any device designed for installation outside of buildings on customers' premises and subject to exposure to the weather, shall NOT be capable of direct plug connection to the network.
* The BT jackpoint is not suitable for external use due to its lack of corrosion protection.
(2) Telecom's standard installation practice is for fixed wiring from the device to be BT plug connected within the building.
(3) The cable used to connect any exterior-mounted device to the internal building cabling shall be of a suitable type for the environmental conditions. This implies the need for relatively thick insulation and sheathing. For this reason, all such devices shall have terminals suitable for connection of heavier weather resistant cable.
* The most suitable means of connection is to terminate the external cable from the device on a terminal block mounted adjacent to, or within the mounting box of a standard jackpoint which is part of the internal premises cabling within the building. A flying lead with one end connected to this terminal block, can have a BT plug on the other end which inserts into the standard jackpoint.
10.9
Other jackpoint connections
(1) For connection to analogue leased lines, the modular connection arrangement shown in Technical Document TNA 102, clause 9.3(3) is recommended.
* This is the standard 8-way plug and socket commonly known as 'RJ45'. Commercial building cabling compliant with AS/NZS 3080 uses this type of socket.
(2) For connection of proprietary interfaces such as the extension phones on some key systems and PABX's, the 4/6-way North American modular plug and socket is recommended where only 2-pair or 3-pair cable is installed.
(3) It is strongly recommended that the BT plug and socket arrangement is not used for either of the above applications. This will avoid the confusion of PSTN telephones or other devices (having BT plugs) being incorrectly connected to the wrong interface.
