How much action will they see?: ISDN power concerns contribute to copper pair shortages-and keep costs up. Several new products may offer relief-but currently are getting only limited play

ISDN is the highest bandwidth connection available for most residential users. By converting a twisted pair copper phone line into a 128 kb/s digital connection, basic rate ISDN offers significantly more bandwidth than a conventional modem-and, unlike a conventional modem, it can simultaneously carry voice and data signals.

Yet ISDN's penetration rates are still very low. Configuration difficulties, which industry groups have begun to address, certainly have contributed to ISDN's lack of appeal. Another key issue, however, has been the fact that ISDN does not draw its power from the central office, as with conventional telephone service, but instead must be powered at the customer premises.

This means that if a power outage occurs in a customer's home, the ISDN line goes out. Although rechargeable power supplies are an option for backup, they have not been popular-perhaps because telephone companies have encouraged ISDN customers to keep a conventional voice line for "lifeline" service.

"We have always recommended to people not to rely on ISDN as a primary service because in an emergency, you would be out of primary phone service and couldn't call 911," says Tom Bayless, director of ISDN for SBC Communications. "One of the first requirements we have of vendors today is that if the service is AC-powered, there has to be some kind of lifeline support that keeps the analog line up."

Complicating matters is the fact that telephone networks conventionally have been engineered for only 1.2 lines per residence. The need for an extra line for ISDN homes-combined with increased demand for second lines for teenagers, modems and fax machines-can sometimes lead to a shortage of copper pairs. The need to have an analog line in addition to an ISDN line also reduces ISDN's attractiveness because it keeps the cost up.

As a spinoff of development efforts to achieve higher bandwidth using digital subscriber line (DSL) technology, a number of manufacturers recently have introduced products that may help address some of these issues for ISDN. XtendPlus from Telmax Communications, the Alchemy product from Wescom and GDSL Plus from GoDigital all can deliver basic rate ISDN plus POTS over a single pair of copper wires from the CO (Figure 1).

GoDigital also offers the GDSL2 and GDSL2 Plus models. Both of these devices offer two ISDN lines over a single copper pair-with and without POTS, respectively.

Solving copper shortages All three solutions require a line card, which is installed in the CO, and a network interface device, which is installed at the point of demarcation at the customer premises (Figure 2). The line card plugs into the same rack that is routinely used for digitally added main lines (DAMLs).

Customers use a conventional phone in addition to any modem or terminal adapter that supports conventional ISDN service. If the network interface device fails, the customer still has an operational analog line.

GoDigital's GDSL Plus solution costs about $600. The Wescom solution costs somewhat more, and XtendPlus is sold on a contract basis and is competitively priced.

Finding a spare pair to support ISDN is a problem in 10% to 20% of installations today, according to Paul Kaliher, director of Wescom's DSL business unit. For those situations, single-pair ISDN plus POTS is an economical alternative.

Bruce Young, Telmax co-founder and chief technical officer, agrees with the lower number, but Frank Akers, GoDigital's chief executive officer, says problem ISDN installations represent about 20% of the total.

With hard-to-fit ISDN customers, "the engineers either have to go out and trench up the front yard to bring in another pair of wires or do an outside plant job and put some cable in up your street," says SBC's Bayless. Such work costs money, takes time and annoys customers, he says.

"They just didn't design many neighborhoods for multiple lines, which causes us to have about 10% of our lines in the hold position," says Bayless. "That makes customers mad because it causes long delays."

Both SBC and BellSouth are testing single-pair ISDN plus POTS solutions, hoping that such solutions will enable them to serve their customers in a more timely fashion. "This would allow us to put a piece of electronics at your house the next day with a matching pair at the [CO] and turn on your ISDN service quickly, rather than waiting three months to build an addition to the network," says Ken Hartsfield, manager of ISDN architecture at BellSouth.

Using single-pair ISDN plus POTS products under test conditions has virtually eliminated the months-long wait some customers have had to endure, Bayless says. Installation now takes 10 to 15 days instead of several weeks or even months.

This is especially beneficial for SBC, which must refund the customer's $125 installation charge if the line is not installed within a certain time frame. "This is a way of assuring that I won't have to refund the installation fee," says Bayless.

Another advantage of all three single-pair ISDN plus POTS solutions is that they extend ISDN's range.

"There are a few different ways to serve ISDN. One way is to do it on a copper pair, but you can only do it for a certain physical distance before you have to use a repeater and continue with a copper pair. Then you have to unload the copper pair," explains Hartsfield. "That is a big barrier in the loop, where you have to put load coils on the copper pairs of everybody who sits more than 18 kilofeet from the [CO]."

The single-pair ISDN plus POTS products offer a simpler solution for serving distant customers, particularly if copper pairs are in short supply.

Another consideration for BellSouth was its digital loop carrier system. "If that wasn't compatible, it would cost us up to $30,000 to make the system compatible just to serve one ISDN customer," Hartsfield says.

The solution, now in test mode, involves systems like those from Wescom, Telmax and GoDigital that enable Hartsfield and his team to bypass BellSouth's embedded DLC system.

Wescom's system boosts ISDN's range by using discrete multitone as an alternative to the 2B1Q line coding traditionally used with ISDN. GoDigital and Telmax use 2B1Q but extend ISDN's range by using the 2B1Q line code more efficiently, proponents say.

More widespread play? Because products such as those from Wescom, Telmax and GoDigital enable carriers to deliver ISDN plus POTS over a single copper pair, carriers eventually may consider pricing it lower than the same services delivered over two pair.

"It is a small thing that could be a big thing," predicts Brett Azuma, director and principal analyst for telecommunications at Dataquest. "It gives the telcos an additional way of deploying service at reduced cost and could even enable them to reduce service time. In addition, the copper portion of their tariffs could be reduced or removed altogether."

While declining to estimate how much of a cost reduction carriers might offer, Azuma points out that when companies have built their tariffs in the past, they have had to separate the pieces that could be broken out. "The copper facility is one piece of the price of the line and generally accounts for about one-third of the tariff," says Azuma. "Then you've got the features on top of that, and ISDN has been defined as one of the features, at least for some carriers. If you can eliminate or noticeably reduce the cost of the copper facility, you can start reducing your tariff."

While declining to mention names, Telmax's Young says some carriers have plans in the works to reduce the cost of ISDN plus POTS when both services are delivered over a single pair. The goal would be to sell more ISDN lines through more attractive pricing.

GoDigital's Akers is more skeptical about whether telcos will choose that route. He says one local exchange carrier considered reducing the cost of ISDN plus POTS by $8.50 a month when those services were delivered over a single pair, but the idea was scrapped because customers already receiving ISDN and POTS over separate lines also would have asked for a discount.

Bayless says the up-front costs of single-pair ISDN plus POTS are still too high to consider reducing the tariff.

"It just isn't a slam-dunk from an economic standpoint. The jury is not in yet," says Bayless. Widespread deployment will require this type of product to be priced so that it becomes an economical alternative for more than just problem installations, he says.

"These companies are going to have to decide if they want this to be the solution of choice for every ISDN line. If these devices are priced too high, carriers will only use them when things get ugly," says Bayless.

BellSouth is also taking a conservative approach. Because of the system's cost and untried nature, the carrier plans to use the technology-at least for now-on an exception basis.

"We plan to use it much like we have used the DAML in the past: when a customer asks for a second line at his house and we have severe network congestion," says Hartsfield. "I can put a DAML out there and suddenly you have two POTS lines falling out of this piece of electronics on the same copper pair. I envision this service working the same way. If we can't get a copper pair to your house for your ISDN order, we will put this piece of electronics at the premises and provision both your POTS line and your requested ISDN line on the same copper pair that heretofore your POTS line worked on."

Will the cost of single-pair ISDN plus POTS come down? Without making a specific prediction, Kaliher seems optimistic. He cites the example of high-bit rate DSL (HDSL), perhaps the most mature of DSL-based devices. A few years ago, HDSL was selling for around $5000. Today its cost is less than $1000.

Telmax's Young believes the appeal of single-pair ISDN plus POTS also will increase because, as incumbent LECs are required to make local loops available to competitors, they will eventually seek to conserve them. He cites the example of Bell Atlantic, which agreed to reserve a certain percentage of its local loops for resale to competitors as a condition for acquiring Nynex. The merged company now has the motivation to use its own loops as efficiently as possible, says Young.

Until the percentage of local copper other carriers must reserve for customers is determined, however, Young cautions that incumbent LECs may be motivated not to use this product except in problem situations. "Now it's to the advantage of the [Bell companies] to say, 'Oh gee, I don't have any copper,'" says Young.

Some industry players have other reservations.

"You are putting a lot of demand on the central office switch-more than the switch is accustomed to handling," charges Marc Hornacek, global digital product director at Motorola.

And as manufacturers gear up for a widespread release of higher-speed access technologies, such as asymmetrical DSL, another concern is whether customers will continue to use ISDN for a long enough time period for carriers to recoup their investment in the GoDigital, Telmax or Wescom products.

"If the customer base is going to jump on and off on a frequent basis, the return on investment would be too high for carriers to recoup their investments in this technology," Azuma posits. Whether it will succeed "really depends on customers hanging around for a couple of years," says Azuma.

Such factors also will determine whether the single-pair ISDN plus POTS solutions will get more play-or whether they will remain on the sidelines, called in only to address special situations.