Voice
Communication in Business Volume 2
Essays on telecommunications,
1981-2002
I have
always been impressed at the way nobody outside of the telephone
business has any grasp at all of "life cycle costing," or what the
total cost of ownership of anything over its life actually is. When
The Government insisted that all of us had to own the telephone
equipment on our premises and took away our freedom to rent from the
telephone company, making lease-vs.-buy decisions became very
important.
But it
also became important for people selling PBXs rather than selling
service rendered by a PBX to understand how to finance after sale
support. I wrote this for the September, 1989 Business
Communications Review to examine the situation. It is an article
I am quite proud of.
The PBX and
Downstream Dollars
(Business Communications Review, 1989)
Back when Carterfone was
new, the technical press was full of articles about how much
companies were going to save by owning their own PBXs and getting
out from under the yoke of monthly payments to the telephone
company. The financial analysis to support this, if it existed at
all, usually assumed writing off the PBX purchase in ten years or
less, and then comparing the "cost-free" years in the rest of the
twenty year study period with what would have been paid to the telco
in monthly charges, adjusted for healthy tariff increases.
Today, twenty years
later, one wonders how many of those early PBXs made it to 1989 and,
if they did, just how cost-free their latter years turned out to be.
Did anyone ever follow up with real costs and actual experiences? In
particular, how many of these owned PBXs were able to get
maintenance and repair at any price, considering the high mortality
rate of vendors and manufacturers, and the even higher rate at which
both move on to more lucrative product lines?
The problem with
estimates based on "it's all paid for" is that profit from the
initial sale, by itself, is not enough to insure the continuing
existence of a service organization, and a one-time bargain can lead
to long-range disaster. When rental from the telephone company
included maintenance, and the PUC allowed the customer to withhold
the rent when the system did not perform, there was both a financial
source and a strong motive to keep the system working. Without such
down-stream dollars (and the right to withhold them for cause),
there is little assurance that an owned system can realize its
useful life.
When an industry changes
from offering a continuing service to selling, once and for all, a
product, the need for continuing sales becomes evident. This creates
conflicting requirements: equipment must have a short enough life to
encourage resale, but a long enough life to discourage the customer
from selecting replacement from a competitor. There are two ways of
dealing with the problem. The first is to continually offer new
models as with cars, playing upon the customer's fear of
obsolescence, while the second is to keep adding a continuous string
of upgrades, improvements and adjuncts, all of which can be sold at
a profit to a now-captive audience. Stored program control seems
designed to give special support to the latter, while advances in
electronics make possible the former.
In a saturated market,
when new sales are limited in spite of exotic new chips, something
has to give. Perhaps the most important things happening in the PBX
field today are the various approaches being taken by PBX
manufacturers and vendors to convert their installed base from a
liability to a source of continuing revenue. The purchase of Rolm by
Siemens suggests just how important installed base has suddenly
become. The customer will certainly benefit from this after-sale
attention, but the "cost-free years" are gone forever.
Replacing The PBX
The PBX interconnect
business got off in an unduly optimistic growth spurt while the
older SXS electromechanical PBXs were being replaced. Fortunately
for the new order, the biggest selling PBXs were only a step ahead
and their replacement is making possible the second but much smaller
sales wave we are riding today: the PAM Dimension from AT&T, the
space division SX-200 from Mitel, the much larger 4-wire space
division CBX from Danray (backbone switch of the early long distance
companies), the delta-mod D1000 or D1200 (depending on who sold it)
from Harris Digital Telephone Systems, and the non-telecom linear
PCM of the Rolm CBX. All of these made a second round of replacement
possible when it became as obvious to customers as it had always
been to Northern Telecom with its SL-1, GTE with its GTD series,
Stromberg Carlson (now Memorex-Telex) with its DBX, and Wescom with
its 580 that the only way electronic switching could cover larger
size ranges was to be digital, and the only kind of digital that
made sense was the kind already extensively used for transmission in
the public telephone network.
It goes without saying
that using the digital of T Carrier in its switching mechanism,
although necessary for some sort of long-range effectiveness, was by
no means sufficient to insure PBX success. Why did GTE change from
GTD to Omni? Where are the Wescom 580, the CXC Rose, the Ztel, the
Cyber Digital and various others today? What has happened to the
NEAX 22, which was at least partially T-carrier based?
Fork-lift upgrades.
Eventually, AT&T bit the bullet and introduced Systems 85, 75, and
25 as "fork-lift" replacements for the Dimensions. Somewhat later,
when Rolm and IBM braved a fork-lift replacement of the CBX with the
9751, AT&T criticized them roundly for doing what AT&T had just
accomplished more or less successfully. In both instances, the
availability of such fork-lift upgrades have benefited from the new
replacement market; they have also been a major factor in creating
the "secondary market." Today, used PBXs, like used cars, offer an
additional opportunity for sales.
Migration paths.
An alternative to the folk-lift upgrade is the "migration path." A
migration path, when properly planned, allows a small system to grow
into a large one, a simple system into one with sophisticated
capabilities, and a new system to be "backwards compatible" with old
ones so that older hardware (particularly circuit boards) need not
be thrown away. Because Northern Telecom was one of the few to make
the right architectural choices initially, the SL-1 has followed
quite skillfully a meaningful migration path as it doubled the port
densities of its cards, increased and improved its switching
capability, changed its packaging, took advantage of larger memory
chips, and made a continuing series of program upgrades.
Mitel had a harder task,
but found an ingenious migration path from its space division
switches to the digital world. Existing analog shelves have 31
speech paths which can be used by analog telephones for intrashelf
connections and, via digital converters, to a 32-channel multiplexed
link to a central switch for connection to other analog shelves or
to new digital shelves.
Many manufacturers had
to make a change from older technologies but, once the change was
made, planned for further migration and growth in a reasonable way.
Siemens uses the same processor, software and circuit cards in all
its Saturns, from smallest to largest, and the new Hitachi HCX5000
grows from small to large on a shelf by shelf basis. The Ericsson
MD110 can grow from one module to two modules back-to-back to a
multi-module system with a central switch. The NEAX 2400 from NEC
can exist as a single shelf, a single cabinet, or a multi-module
system using single cabinets as modules interconnected via a central
switch.
Old telephones sell
new systems. In designing a migration path for PBX hardware,
some of the factors to be considered include preserving the existing
telephone sets and wiring, using the same port cards, using the same
type of cabinets, and using the same processor. Telephone sets seem
to have the greatest impact on the customer. The customer will
apparently migrate more easily to a new PBX, invisible in the back
room, if the highly visible telephones on each desk can be reused.
This is particularly true for customers of Centrex who were forced
to buy the telephone sets on their desks to continue with Centrex
until a PBX could be procured.
For this reason, we
still find most modern systems supporting the venerable 500/2500
type telephone with its single pair wiring, hundred year old power
ringing, and relatively standard signaling. In general, PBXs do not
like to support the related 1A2 key systems, however, because of the
interaction of PBX and key system features. Where multi-button sets
are needed, most PBXs offer proprietary sets that take better
advantage of PBX technology and control capabilities. Unfortunately,
many such sets have preserved the two-wire transmission package of
the 2500 set. For Centrex use, where two-wire loops and switching
are standard, this may make sense, but for use with a modern digital
PBX which can only do 4-wire switching, it made no sense at all to
pass up a chance to go 4-wire to the set and eliminate a major
transmission problem, echo.
In 2-wire analog PBXs
such as the AT&T Dimension and the Mitel SX-200, a rationale for
2-wire transmission for MET sets or Supersets existed. But when
4-wire digital switching was used, as with Rolm and Northern
Telecom, it is hard to understand the reasoning that led to 2-wire
transmission for the ETS-100 and SL-1 sets, respectively. When
second-chance time came, these companies took full advantage of what
they had learned. Both the ROLMphones and the Meridian sets use
4-wire transmission from line card to telephone set, generating
separate paths in each direction for voice, data and control on a
single pair using electronic techniques. (Rolm uses hybrids while
Northern Telecom uses ping-pong bursts). Rolm dropped its ETS-100
sets, but Northern kept the SL-1 sets in its product line.
Even while Rolm was
still defending its linear PCM for switching, it developed the
ROLMphones using standard T-carrier companded coding. Thus when the
Redwood was developed, and followed later by the 9751, the same
family of multi-button sets served all. This simplified
manufacturing, inventory, and training for both vendors and
customers. With single pair wiring, just like that used by 2500
sets, an upgrade from the older CBX could indeed be made simply by
replacing the machine in the back room.
AT&T offers some
interesting examples in keeping existing telephones while migrating
PBXs. The 7200 series, developed for System 85, was enough similar
to the older MET sets so that its line card could run MET sets
already owned. Merlin, however, developed its own sets in the 7300
series, which functioned differently: both 7200 and 7300 sets use
three pair wiring, with one pair for 2-wire analog voice, but the
7200 uses one pair in each direction for signaling and the same two
pairs for power, while the 7300 uses one pair for signaling in both
directions and the third pair for power. Systems 25 and 75 emphasize
the 7300 sets to facilitate Merlin replacement, and now that Systems
75 and 85 are combined into Definity, sets in the 7200 series are
manufacture discontinued. Systems 25, 75 and Definity use many of
the same port cards, so reuse of these cards as well as the 7300
telephone sets helps considerably with migration.
Systems 85 and 75 both
support another series of multi-button electronic sets: the 7400.
These look and act (pretty much) like those in the 7200 and 7300
series, but are completely digital using AT&T's proprietary DCP
(digital communications protocol). DCP is based on two pairs, one
out to the set and one back, with voice, data and control channels
multiplexed onto each pair. System 25 elected not to use these sets
because of their cost; when AT&T recently lowered the price of the
7400 sets to a point well below that of the 7300 series, System 25
was unable to start a migration path which retains digital sets
while replacing the back-room box, although Merlin Plus can do just
this.
Growth and control.
The interaction of growth and system control is a tricky topic.
Obviously, a large system needs a larger data base than a small
system, because it has more telephones and trunks for which it must
store operational information. Thus there is a tendency on the part
of designers to use smaller memories for smaller systems, and
smaller processors as well, because fewer ports will generate fewer
calls per hour. Northern Telecom, which uses proprietary processors
in the SL-1, has a small and a large processor available, but they
apparently run the same software. This makes after-sale support and
technician software training easier. The Rolm/IBM and now Siemens
9751 uses the same processor shelf whether the system is small or
large. A 32-bit processor may seem like overkill at the lower end of
the size range, but the advantage of the same hardware and software,
regardless of system size, has to be a major advantage in after-sale
support.
AT&T, with different
processors in System 85, 75 and 25, has the worst of all possible
worlds. System 85 uses an AT&T proprietary processor, 75 uses an
8086 from Intel, while 25 uses a Motorola 68010. This means that,
even though the software follows the same general idea, it has to be
redone for each system with quirky little differences across the
product line. The Definity, AT&T's attempt to reduce this problem to
some extent by combining Systems 75 and 85 into one system, actually
provides the definitive case study to show how difficult the job
really is.
Definity is designed to
use the same port shelves and the same port cards from its smallest
size to its largest, and to allow existing Systems 75 and 85 to join
it upon upgrade. System 25, although it uses most of the same port
cards as System 75, is not part of this overall plan. Definity
Generic 1, an upgraded System 75, has a new processor shelf with an
80286 replacing the original 8086 to allow expansion to two
cabinets. Generic 2 has a slightly modified System 85 processor and
central switch with individual line modules ("universal modules")
that are very much like System 75s or single-cabinet Generic 1
systems. However, universal modules each use an 8086-based processor
in yet another control shelf, so that they will look to the central
processor just like the module processors in the "traditional
modules" of System 85. Generic 2 software can run both universal
modules and traditional modules with equal ease. This approach does,
indeed, provide a very clever growth and migration path, but will
continue to surprise upgrade customers with slightly different ways
of dealing with the some of the features.
The NEAX 2400 handles
increasing traffic by adding more 8086 processors in parallel,
sharing the load. The much smaller Taderan Coral can arrange to have
two processors running in parallel, again in load sharing rather
than hot standby. Parallel processing increases system capability
and also simplifies continuing operation when a processor fails.
Ericsson and Redcom, a
large and a smaller system using a similar approach, are made up of
individual modules, each of which can handle the ports assigned to
it autonomously. To complete a call to a port on another module,
both broadcast the destination and, when they get a response,
connect to that module and let it complete the call. Either system
can expand simply by adding additional modules, each of which has
its own processor for traffic, its own memory for data base, and its
own switching capability. Because the Ericsson is appreciably
larger, its individual modules are larger and it can use a central
switch for inter-module connections.
Downstream Dollars From
Existing PBXs
Maintenance contracts.
Maintenance contracts are one way for a vendor to continue to
generate downstream dollars after the sale. Usually there is a one
year warranty, but after it expires, the customer may be willing to
pay a fixed fee to be sure of repairs within a given period of time
if they should be needed. The catch here is that modern electronic
equipment is very reliable and does not often break down. Thus the
user may "guts it out," taking a chance on paying for breakdowns if
and when they actually happen.
The economics are fairly
tricky: charge too much for a service contract, and the customer
will not sign, and may not even buy the PBX. Charge too little, and
the cost of rendering the service may exceed the revenue it
produces. In the case of computers, independent service companies
often find a niche here. They offer service contracts for less than
the computer vendor, and pay full price to that same vendor to
actually render the required service for their clients when needed,
playing the odds as service brokers and apparently making a living.
It is quite evident that
a vendor or an independent service organization, sharing a group of
technicians among a number of PBXs, will get better use from the
members of the group than each customer would get from an in-house
technician (just as one big trunk group provides better service than
the same number of trunks used as individuals). Further, the skills
of group members will be kept more active by having a larger pool of
equipment from which to gain experience.
A particularly good
approach is something like AT&T's RMATS. A number of vendors have
taken to offering this kind of preventative maintenance: at a
regular interval, they call up their customers' PBXs and run
diagnostics. This often allows them find incipient problems before
they become acute, and schedule repairs in such a way that emergency
action can be avoided. Most modern PBXs are designed for remote
diagnostics; unfortunately, not all vendors are willing to invest in
the personnel to permit them to take advantage of this capability.
With long distance costs as inexpensive as they are today, one might
hope that the manufacturer, with a highly efficient group of skilled
people at the factory, could run diagnostics all over the country,
alerting vendors to what needs to be done for their customers when
faults are discovered. Any number of approaches along these lines
would not only be a better buy for the customer and a good selling
point for the vendor, but would make the cost of rendering service
less while increasing revenue over the life of the system.
Moves, changes and
updates. Even in the days of the monopoly, when maintenance was
included in the monthly rent, moves, changes and additions were not.
After competition was legalized, these items were viewed as a
particularly good source of income, if one was a vendor, and as a
particularly annoying source of expense, if one was a customer. The
delicate balance between the chance to make money and the ability to
lose the customer was quickly upset by customer awareness and
advances in technology.
It quickly became
evident that saving money by installing minimum amounts of wire at
cutover was poor economy; knowledgeable customers would install
several pairs to every point where a phone might ever be wanted in
the future. Many consider 4-pair wiring terminated in an RJ-45 jack
to be a standard, and modern cross-connect frames, by making clear
the identification of each pair, allow the management of wiring even
by people with little technical training. Again, we have a Catch 22.
If wiring changes are difficult, a vendor may not be able to hire
and train technicians to do the job. However, if they become much
easier, the customer will be willing to take on the job and pay the
vendor nothing.
The same can be said for
modifying station characteristics. Fifteen years ago, memory was so
expensive that programs required to operate a PBX had to be written
very efficiently, usually to fit into 256K or less. There was little
room to make them "user friendly." Thus a well-trained and highly
skilled technician was the only person who could be permitted to
make such modifications as were possible. Indeed, some systems, with
their software in ROM, could not even change the number of an
extension, and class of service was modified by small switches on
port cards.
Today, all this has
changed. The great majority of PBXs have terminals that can modify
the system data base and reconfigure station equipment with
different features, restriction levels, and line pick-ups. Such
terminals present the administrator with menus of possible actions
and station templates to simplify the handling of multi-button sets
without vendor help or expense. Only a few manufacturers and vendors
are hanging on to the $70 an hour sinecure and they will have to
give way before long.
Going a step further at
the station moves level, TeleNova and SRX identify their sets with a
serial number in ROM. When a phone is assigned to a station user,
the data base for that user is established and related to the serial
number of the telephone. Then, wherever the user plugs in, the
system reads the serial number, assigns the appropriate data base to
the port, and, in the TeleNova, supplies the set extension number on
the LCD display. This really makes moves and changes easy and acts
as a good selling point, but it doesn't do much to generate revenue
for the vendor after the sale. It does, of course, require the
customer to stick with proprietary telephone sets.
Software upgrades.
Once a PBX is up and running, software upgrades are a particularly
good source of continuing revenue. Adding features and improving the
more complex ones such as Route Selection are sure winners. The
customer gets to keep the not only the telephones, but the box in
the back room, and yet new wonder are now available. More powerful
processors and inexpensive memory chips of ever-increasing capacity
make possible software structures that, just a few years ago, could
not have even been considered.
Sometimes memory must be
added to accommodate new software, but very often new hardware such
as telephone sets requires new software to function. This chicken
and egg approach can be a powerful tool to lock in user loyalty.
Today, networking and
feature transparency can extend vendor opportunities over a whole
group of PBXs, and an upgrade intended for one will have to be
duplicated in the others. The countervailing force, appreciated more
and more by knowledgeable users, is to replace separate PBXs with
remote switching units or remote modules; this means that only one
PBX and one set of software upgrades requires the attention of the
system administrator. The Northern Telecom SL-1, InteCom IBX and
Ericsson MD110 offer examples of quite different architectures which
can provide this benefit to the customer.
Adding off-line
computers to the PBX. Adding software upgrades to the PBX common
control is just one of several ways that software can bring in
downstream dollars. More and more manufacturers are finding ways to
augment their systems with off-line computers (applications
processors) that provide new features to the PBX or improve the
utility of features already present.
The first small
computers entered the PBX world ten or twelve years ago to allow the
communication manager to take full advantage of call detail
recording. Remember the ZapCall, the Call Quest from Com Dev,
products from Sure and Sykes and Bitek and others? All these were
small computers, based on the 8080, Z80 or 6800 microprocessors.
They plugged into the RS-232 output of the PBX, and, like a printer
or a tape recorder, accepted call records as the PBX put them out.
But they were not passive recorders; they put each record into one
or more bins as they received it, pre-sorting as required, and
printed out the bins on demand as bills and management reports.
When personal computers
became available, they sometimes took over this function. Harris
originally used CP/M based systems, and made CDR bills available on
a daily basis in small hotels and motels. Data collection ran in the
background, and the computer could be used for other functions as
well. Datapoint's brief and unsuccessful effort to break into the
PBX business was highly prophetic: in that concept, the PBX central
processor was just another computer on an ARCnet; as such, it could
send out CDR information to one of the other computers for storage
and processing, obtain information from an off-line directory, etc.
While AT&T, Northern
Telecom, GTE, Rolm and others were busy developing dumb terminals to
act as voice and data telephones, offering a display vastly more
useful than the traditional flashing lights of multi-button sets,
they were bypassed by personal computers that cost less, had more
memory, and could do anything for which software could be written.
With various RS-232
ports designed originally for plugging a dumb terminal into the PBX
control to manage system administration on-line and in real time, it
quickly became evident that a computer could be programmed to
interact the same way, uploading moves, changes and other tasks
previously prepared and edited offline. Today, a number of
independent software companies offer such packages, and the PBX
manufacturers are beginning to see the wisdom of offering something
similar themselves. AT&T developed Manager and Monitor software
packages for the Definity, and Northern Telecom has recently
announced three Meridian Manager software packages developed by
Forte Advanced Management Software, Inc., for handling station
administration, work orders, and traffic reporting. The latter is
particularly useful in that it can translate the SL-1's cryptic
traffic data into readable reports.
Off-line software
support can provide a great improvement in PBX management; the PBX
can use its internal memory primarily for operations, leaving the
human factors interface to the off-line processor. And, of course,
each software release for the PBX has the possibility of generating
additional revenue from the related offline software update. We will
see a lot more of this, not only in the PBX field, but in the local
and toll office area as well.
The automatic call
distribution function can easily be built into a PBX; usually little
is needed but software, particularly if the PBX approaches
non-blocking capability in its switching matrix so that it can
support the high occupancy of ACD agents without having to worry
about traffic balancing. But the ability to deliver calls is only
part of the ACD operation; providing FADS (Force Administration Data
System) capability is also necessary.
FADS or MIS capability
is another natural for an off-line PC which can capture traffic
measurements, even if the PBX records them in hexadecimal, and
present them, enhanced by passage through an off-line data base, to
supervisors and system administrators. With the memory and
processing power of modern PCs, history files can easily be
maintained and graphic presentations of data can be offered in a
variety of forms.
Subtracting data from
the PBX. One of the more obvious ways that a digital PBX could
generate additional revenues for its manufacturer and vendor was to
provide a more efficient way of transmitting data. This was
particularly true when voice was digitized at the telephone set so
that it became a bit-stream that could be multiplexed with a similar
appearing bit stream from a data terminal. This capability, although
present in many PBXs, is not being widely used. Instead, customers
are installing local area networks to tie their PCs together.
Failure of PBX manufacturers and vendors to capitalize on this
capability, particularly when built into a product they have already
sold, is a factor on which many have speculated.
The most likely answer
seems to be that Voice people buy PBXs while Data people buy LANS,
and in neither type of transaction do vendors or customers for one
service know very much about the other. PBX manufacturers, for
instance, insist that small PBXs do not need data capability, while
the average LAN installation ties together something like 8 PCs.
The telephone industry
has had a century to learn how NOT to compete with local area
networks. During most of that time, its objective was to provide
universal service; as a result, everything possible was done to keep
the cost of basic service to a minimum and to use extra features to
generate extra revenue. Touch-Tone is a good example. Designed
originally to speed up call completion and reduce the amount of
central office equipment needed, it was converted into a prestige
feature for which the customer was charged extra.
I have a feeling the
same thing happened to data in digital PBXs. The manufacturers, both
old timers from the telephone industry and newly established
innovators, saw data as a highly desirable feature for which the
customer should be willing to pay a premium. That might have worked
in the old days when the customer had no choice, but today, where
there is a variety of ways to do anything, the customer will not
necessarily share the telephone vendor's concept of "value added."
All too often, to get data capability, the customer has to buy a
voice-data digital telephone that costs more than a 25 inch color
TV. That such costs are unnecessary was demonstrated years ago by
the Lexar PBX (now the Memorex-Telex 1001) which offered digital
telephones economical enough to be used in hotel rooms. When the
incremental cost of adding data capability to a PBX is less than the
per-port cost of a LAN, the PBX may yet become a contender. Proper
design and pricing of the data interface is clearly a major factor
which has yet to be adequately addressed.
The speed of LANS may or
may not be a factor. Northern Telecom has moved its Packet Transport
Equipment away from the SL-1 and set it up as a stand-alone local
area network called Meridian LANSTAR. LANSTAR uses two pair wiring
from line port to data terminal at 2.5 Mb/s, and has 40 Mb/s of
LAN-type bandwidth to get from one line port to another within the
central cabinet. As PTE on the SL-1, PBX customers did not rush out
to buy it. If data customers buy it as the Meridian LANSTAR, we may
begin to see what it takes to sell office data systems.
InteCom is another PBX
manufacturer that built in high-speed LAN capabilities, running
almost 1 Mb/s to the work location and providing high-speed packet
switching internally. InteCom's LANmark data features can access
Ethernet LANS as well as terminals and computers, with no apparent
degradation in throughput. But Wang, after buying InteCom to build
PBXs to be controllers of the office of the future, is having
considerable difficulty selling the idea and may end up selling
InteCom.
One of the purposes of
LANs today seems to be to allow a user to call up a file from a hard
disk on another as easily as from his or her own. This requires a
protocol to do the job, something Datapoint demonstrated in ARCnet
ten years ago. But such protocols, which have to identify the other
file server from which they are to obtain the data, as well as the
name of the file itself, are much easier to set up for a small
number of terminals than a large number. Because most LANS serve an
order of magnitude fewer information sources than do PBXs, protocols
are easy. When the number of sources becomes as great as the present
number of telephones on a private PBX network, a suitable numbering
plan and protocol to use it will be appreciably more complex. We can
anticipate abbreviated dialing and speed calling to be a major
factor in future protocols establishing data connections as the
number of choices increases. And then, perhaps the voice-data PBX
will come into its own.
Revenue from new
telephones on existing PBXs. For many years, vendors of
electronic PBXs, trying to show savings over older SXS PBXs,
insisted that single line phones with an infinite array of stored
program features could permit business customers to operate with
residential single line telephones. Although the concept seemed
reasonable, it didn't work in practice. The replacement of single
line phones with multi-button electronic sets (along with new the
line-card required to support them) turned out to be quite
lucrative, and has led manufacturers to produce several generations
of electronic sets at relatively high cost to generate continuing
revenue from their installed base of PBXs. Obviously, a new phone
may well need a different line card, and, if its hardware is
designed to support new features, it will probably need a new
software release to get those features to work. It follows that the
installed PBX base may well be a major factor in keeping your vendor
solvent until you finally need to buy a whole new system.
Early electronic sets
anticipated ISDN by using a separate signaling channel to tell the
common control which buttons had been pushed, and to allow the
common control to tell them which lamps to light to guide the user.
Buttons and lamps could be used for different calls, and they could
also be used to invoke and provide information about features. But
anything done in plastic, such as telephone sets, needs to have the
minimum number of separate parts such as buttons. Thus a variety of
displays, at first numeric and then alpha-numeric, was developed to
increase the capabilities of telephones without adding more buttons.
Speed calling, for instance, needed only one button to invoke the
feature by displaying a set of names with the matching abbreviated
dialing number next to them. The user could page through the list,
find the desired name, and then dial the one or two digit code
specified.
The next step was to add
soft function keys to an alphanumeric display so that the display
could spell out which features the soft function keys could activate
at any particular instant. It might show the number of a ringing
phone and which button to push to get the call, or it might prompt
the user through the process of forwarding calls to another
extension. The use of soft function keys, pioneered by Mitel,
TeleNova and others, is now widely available. Even Northern Telecom,
for years offering only numeric displays on some of its original
SL-1 phones, and nothing on its early Meridian sets, now has a whole
group of digital phones with LCD displays capable of providing
prompts in a variety of different languages.
All these phones and
their protocols are proprietary; because they are such a good source
of revenue, manufacturers can hardly be blamed for not wanting to
give the Orient another boost via an open protocol. But there are
other factors, in addition to ISDN, that may force open protocols
into existence. Voice mail is perhaps the most obvious of these.
Rolm, AT&T, Northern
Telecom, NEC and other companies have developed their own voice mail
systems that can be closely integrated with their PBXs, while
stand-alone systems from VMX, Octel and others are also available.
These systems usually appear to the PBX as a group of analog lines
to which calls are forwarded when the called line is busy or does
not answer. There is usually a data link from the voice mail's
control to the PBX common control to facilitate identifying the
mailbox in which a call is to be stored, telling the common control
which message waiting lamp to light, etc. Within the voice mail
system, the message is digitized once again using compression
techniques and stored on a hard disk.
In its simplest form, a
voice mail system is a multi-port shared answering machine; however,
it can do a great many other things such as sending messages to
other people's mail boxes, dispatching voice memos to mail boxes of
people on a mailing list, appending comments on a message from party
A and sending the results to party B, etc., etc. It can also act as
an automated attendant, provide voice menus to enable users with
DTMF phones to buy things, register for college courses, or ask for
special services. To fully utilize all these various capabilities,
voice mail needs as many feature codes, dialed by the user, as the
2500 telephone sets ever did when they were trying to replace 1A2
key equipment. Not surprisingly, it is just as hard to use 20 or 30
feature codes for voice mail as it was for phone features.
So the alphanumeric
displays with their soft function keys on the newer telephone sets
now have greatly added potential: they can prompt the user through
the operation of associated systems such as voice mail the same way
they do with PBX features. This requires the voice mail and the PBX
controls to talk to each other so that the user can be informed of
what voice mail options are available, and user generated
information can be returned to the voice mail system once the
decision is made.
Northern Telecom can do
this for its own Meridian Mail, but not for voice mail systems from
other manufacturers. On the other hand, TeleNova has made the
protocol for the display in its electronic sets available to voice
mail manufacturers so that they can use the TeleNova phone for their
prompts. A highly desirable development in voice mail would be for
the voice mail ports themselves to appear to the PBX as digital
rather than analog telephones. This would eliminate several A/D
conversions but, more to the point, would make the D-like control
channel available to the voice mail on every connection. Then the
PBX could tell the voice mail the identity of the called party just
as it displays to a digital set the point from which the call was
forwarded, and could accept signals from the voice mail to light the
MW lamp, much as it does from a digital phone in a manned message
center. Octel has cracked the codes on the signaling channels of
some PBXs to do this, but for the general case, we will apparently
have to wait for the open protocols of ISDN.
Conclusions
The need to generate
continuing revenue from an installed base of customers is generally
considered by manufacturers and vendors to be vital in the PBX
market today. One of the most obvious sources of revenue is
upgrading the one part of the telephone system the user comes in
contact with all the time: the telephone set itself. The large
number of very expensive telephone sets offered by PBX manufacturers
suggests the strategy is working. That all these sets are
proprietary and their protocols are not generally known to outsiders
protects a valuable source of revenue.
When ISDN gets here, and
is finally able to do things the proprietary PBX telephones have
been doing for years, it will be an open protocol. This means that
customers will ultimately be able to buy telephones anywhere,
probably at a considerable saving.
The question that arises
is this: will the opportunity for customer to buy low cost ISDN
telephones from other sources reduce the revenue needed by PBX
vendors and manufacturers to provide after sale support for their
products? If so, will this make RENTED Centrex, with its assured
funding, a more reliable option? Or will the greater capability of
PBXs be adequately supported by downstream dollars from software,
computer and data upgrades to keep the PBX viable in the ISDN world?
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