The following are the only supported scenarios in which wired extensions and devices outside the main building can be connected to the IP Office system. In these scenarios, additional protection, in the form of protective grounding and surge protectors, must be fitted.

icon_warning WARNING
The fitting of additional protection does not remove the risk of damage. It merely reduces the chances of damage.


Only ports on IP Office external expansion modules are supported. Out-of-building connection to ports on base cards in the control unit is not supported.

Cables of different types, for example trunk lines, phone extensions, ground and power connections, should be kept separate.

All cabling between buildings should be enclosed in grounded ducting. Ideally this ducting should be buried.

A Primary Protection Box must be provided at the point where the cables enter the building. This should be three point protection (tip, ring and ground). Typically this would be gas tube protection provided by the local telephone company. The ground wire must be thick enough to handle all the lines being affected by indirect strike at the same time.

Connection Type

Protection Device Type


Analog Phone Extensions
Phones External expansion module (POT or PHONE) ports only.

IP Office Barrier Box
Supports a single connection. Maximum of 16 on any expansion module.

Connection from the external expansion module to the phone must be via a surge protector at each end and via the primary protection point in each building.

The IP Office external expansion modules, control unit and IROB devices must be connected to the protective ground point in their building.

The between building connection must be via earthed ducting, preferable underground. The cable must not be exposed externally at any point.

DS Phone Extensions

Supports up to 4 connections. This device was previously referred to as the Avaya 146E.

Analog Trunks

ITW Linx MCO4x4
Supports up to 4 two-wire lines. This device was previously referred to as the Avaya 146C.

For installations in the Republic of South Africa, the fitting of surge protection on analog trunks is a requirement.

For other locations where the risk of lightning strikes is felt to be high, additional protection of incoming analog trunks is recommended.

External Output Switch

Supports up to 4 connections. This device was previously referred to as the Avaya 146E.

Connections from an IP Office Ext O/P port to an external relay device must be via a surge protector.

When using the MDS2 on the Ext O/P port, use only the Line 1 and Equipment 1 jacks, do not use the Line 2 or Equipment 2 jacks.

The towerMAX range of devices are supplied by ITWLinx (