Chapter 14: Managing PBX and Key Telephone Equipment

Overview

This chapter discusses PBXs, key telephone systems, and hybrids and their role in connecting users for voice communications internally and externally. Customer premises switching equipment has seen significant improvements and cost reductions due to the advent of new low-cost electronics. The differences in customer premises switching equipment and the system features of major PBX systems are outlined. This includes the main factors in choosing and administering a PBX.

Differences in Switching System Types

·        Key systems are standard telephone systems that access outgoing trunks by pushing a button on the telephone itself. Key systems are ideal for offices with fewer than 25 stations. Users can transfer calls over intercom paths but automatic call transfer is not available

·        A PBX is a highly specialized time-shared computer with numerous ports. It can be programmed so that specialized applications can run on it. Automatic call distribution is supported as well as remote switching. These systems are ideal in offices where there are 125 or more telephone stations. PBXs offer many important features that these larger organizations need

·        Hybrid systems are used where there is between 25 and 125 stations and there is not a strong case for a PBX or a key system. They possess some characteristics of both a PBX and a key system

Major PBX System Features

Automatic Route Selection

Also called Least-cost accounting, this feature can analyze the digits dialed on the telephone and determine what the least-expensive way of sending it would be based on trunk groups available, time of day, and digits dialed

·        Message-handling problems are reduced when using a PBX
·        Automatic callback allows a user to camp on a line when the line is busy and ring both parties when the line is free
·        Message display features are also available on a PBX allowing the user to see such things as an internal calling party’s name or an external caller identity

This category includes features such as voice mail, automatic call distribution, call accounting, and interactive voice response.

A remote switch unit (RSU) is a cabinet that contains line cards which is located some distance from the main processor. This is less expensive than having an additional PBX and the RSU can be administered from the main system. Features are the same as those in the main system

Traffic Usage Measuring Equipment

·        This is an important feature in choosing a PBX. Data is provided by the PBX that can aid in cost-efficiency. This may include things like the percentage of outgoing calls not carried because of blockage or the percentage of time that all trunks were busy

·        The way this data is reported is important. Information in formatted form is easier for a person to understand than unformatted text

Station Loop Range

·        Station range is often expressed in distance from the PBX to the telephone station. In general, most digital phones have the least amount of station range with 1 kilometer or less. Range extenders can be used to increase the range

Remote Maintenance and Diagnostics

Most PBXs are capable of being diagnosed by a remote maintenance center. This could include a center operated by the vendor or the manufacturer

Virtual Office Support

This service is beneficial for telecommuters. It allows users to log in and have PBX services transferred to a remote telephone

Emergency Number Support

PBXs are responsible for routing emergency numbers. Important information such as station location can be sent over the line to the emergency service if the PBX supports it

Direct Digital Trunk Interface

It is possible to connect a T-1 line directly from the IXC to the PBX. This can reduce the cost of the PBX because it could eliminate individual analog trunks

Station Sets

The telephone sets used at each individual station are important to the effectiveness of the PBX. Some stations have displays, some have extra secretarial functions. These are important in selecting a PBX

Direct Inward System Access

Direct Inward Systems Access (DISA) allows users from the outside to access features of the PBX such as long-distance services and dial dictation

Direct Inward Dialing

This feature allows callers to bypass an attendant by dialing the extension of a station set directly

Class of Service and Restriction

PBXs can offer certain features to authorized users or groups. This authorization can be in the form of classes of service (COS) or classes of restrictions (COR)

Attendant Console Features

Certain features for attendants are available on PBXs. An attendant can “camp” a caller on a busy line so that the call can be completed when the line is no longer busy. Digital display features are also available on some PBXs. This tells the operator a great deal about calls that are returning to their console for further attention

Call Coverage

This feature handles calls that are unable to be answered by the station. Calls may be sent to an answering position, voice mail, or a console operator

Computer Telephone Integration

Most PBXs offer a computer interface link. This feature allows the computer and the PBX to exchange instructions and call progress signals

Stations on a PBX can be set to a different ringing tone to distinguish which telephone in an office setting is ringing

Most PBXs can provide a modem pool for centralized use. Modems can be given the restrictions and features of the PBX

In case of power failure or PBX processor failure, trunk lines can be transferred to selected stations

Forced Authorization Codes

PBXs can be setup so that a user has to enter an authorization code. This code then identifies the call so that it can be billed properly. This might be used in a law firm where calls are charged to client’s accounts

PBX Administration

·        All PBXs provide an interface for administration
·        PBXs differ in the type of user interface offered. Ease of making changes to the PBX is an important consideration
·        Every office should have someone trained to perform basic station changes

Selecting Key Telephone Systems

·        Many Key telephone systems have PBX type features
·        Many key systems are sold with voice mail and some can display calling line identification
·        Vendors should quote systems by the number of stations that constitutes maximum capacity

Telephone Sets

Most key systems use proprietary equipment. Proprietary stations may be compatible with larger key systems or even PBXs from the same manufacturer

Expansion Capability

Key systems have electronic station cards for communication over a thin cable. Stations are terminated in line cards, which usually are 4 or 16 stations each. To have more stations more cards need to be added

Hands Free Answer and Intercom

Most modern key systems have an internal paging feature that allows two way conversation over a speakerphone

Flash Button Call Transfer

A flash button allows the user to flash the central office. It prepares the key system to receive a code. This feature allows calls to be transferred to another line or a cell phone. This feature is not available on PBXs. A PBX must use the outgoing call feature which then will tie up two trunk lines. The key system will allow the first trunk to be released when the call is transferred

Switching System Selection Considerations

·        When making a switching system selection you must understand your requirements thoroughly.

·        Talk to users and find out what they like and dislike

·        Talk to higher management and find out about projected growth

·        Switching system vendors should be asked to demonstrate their systems

·        There are two primary factors in choosing a system. These are vendor support and product value

Vendor Support

The following are important considerations when selecting a vendor

·        Make sure the vendor has sufficient support staff
·        Make sure the vendor has a satisfactory record of support
·        Find out what support features the vendor includes
·        See if the vendor has a remote maintenance center
·        Check if the vendor has specialists for different functions

Product Value

The following are important considerations when checking for product value

·        Check where the product is in its life cycle. Is it a new product or an old one destined for replacement?
·        Examine the record of the manufacturer. Do they have a record for leading or keeping pace with technology?
·        How often is new software released?