In the United States, simple types of analog telecommunication terminal equipment (TTE), such as telephone sets, data modems, and facsimile machines, use a similar analog public-switched telephone-network (PSTN) interface. That interface also applies to more complex equipment, such as interactive voice-response encryption terminals. However, the US standard, FCC Part 68, seeks primarily to protect the telephone network, whereas the European standards add performance requirements. European analog standards add telecommunications performance, electromagnetic compatibility (EMC), and safety issues to their requirements.

As you begin obtaining the relevant specifications, you quickly realize that they differ significantly from the US standards. Western European approval requirements for analog TTE include safety standards in some countries, EMC standards in some countries, and telecommunications-performance standards in nearly every country. In every case, the standards are stricter than those in the United States. Worse, if the product fails a test in any country, the country grants no approval.

You also notice that some countries have unique approval requirements. Attempting to meet these unique requirements after the basic design is complete can ruin an already-slipping schedule. These requirements typically need long lead times to implement and difficult testing to verify compliance. As a result, a vendor that adds target countries to its marketing list can complicate the design of the company's once-simple US product. Identifying approval design requirements early is essential to meeting different countries' sometimes-conflicting specifications.

Unfortunately, too many designers implement projects with only US specifications in mind and address the European requirements later. This scenario occurs even if a company intended the product for the European market after an initial US kickoff. Because companies must meet schedules and control costs, often with limited resources, companies often overlook regulatory approval requirements. To budget their resources, vendors must identify the time and cost of designing to meet these requirements. Many vendors ignore the fact that redesigning to meet European approvals is expensive.

In many European countries, three organizations participate in approving analog TTE. Standards bodies write the telecommunication standards, test labs use the standards to test equipment, and Notified Bodies review the test reports and issue the approval certificate. These three agencies were once part of each company's Post, Telephone, and Telegraph governmental agency, but that situation has changed. Privatization is causing the standards bodies to abandon national standards and adopt the European norms (ENs), except in analog TTE, in which national standards remain. The test labs of various countries are now competing to provide services for other countries. The Notified Bodies, however, remain part of the government.

This scattered and changing regulatory landscape complicates the next step in planning for type approval: obtaining the pertinent standards. Some common standards for analog TTE include:

• Safety: information-technology equipment (ITE), EN 60950 safety creepage and clearance
• EMC: emissions and immunity, EN 55022
• Telecommunications and TTE performance: National Technical Regulations (NTRs)

Table 1 lists full names of standards. Unfortunately, vendors cannot obtain all the required documentation for all countries from a single source. The most extensive selection of translated specifications comes from the British Standards Institute. For some standards, however, you must go to each country's standards body. Even doing that may not be enough. For example, PSTN specifications may not exist for equipment with unique features or using a new technology.

Just a few unique European requirements follow:

• 16-kHz German and 12-kHz Swiss billing tone filter
• French line-current limiting, black listing on repeat dial, and T.4 and T.30 facsimile protocol
• and UK factory quality assurance, British Approvals Board for Telecommunication (BABT) 340.

For some equipment, more than one standard applies. In the United Kingdom, for example, vendors of telephone sets with speaker phones must test both the telephone and the speaker-phone standards. Some countries accept the requirements in European Norms (ENs); others add NTRs or country requirements to the ENs. For example, in France, vendors selling equipment tested on RFI to EN 55022 need additional tests to meet parts of the NF C 98-020 French standard on EMC.

If your company is part of a large multinational corporation, you can access a valuable resource-sharing documents among departments. Pay attention to the issue date of borrowed documents, however. A specification that is only a few years old may be out of date.

The effort to obtain the most current document can pay off. Europe is moving toward relaxing approval requirements, so a more recent standard may be easier to meet. Also, be aware of draft specifications. Drafts are not official documents until final publication, but they can indicate the direction in which the standards body wants to proceed. Knowing what's coming might save you a redesign.

Although European specifications are changing rapidly, industry has a voice in their implementation. To avoid a business environment in which specification changes occur during design or even during submission of an application for testing, industry has persuaded the standards bodies to use a long transition period for new standards. The transition allows those who have started designs meeting old specifications to get their products tested and allows those who want to use the latest specification to do so.

For example, the July 1994 newsletter of BABT states that a transition is occurring from current standards to NTRs. The transition will not affect approval schemes based on harmonized European standards, including Global System for Mobile, personal communications network, and integrated-services digital-network basic and primary access. According to the newsletter, the NTRs have been in effect since Aug 1, 1994, but existing approval schemes will remain available at least until the end of this year. The newsletter also describes a draft NTR for nonvoice terminals, which represents a national equivalent to the European Technical Basis for Regulation. You can obtain a free copy of the newsletter and copies of the draft, BABT/TC/132, from Jean Gritt at BABT, fax 011 44 932 229756; direct technical queries to Martin Sampson.

Some simple examples illustrate the complexity that European regulatory standards add to analog TTE designs. Consider the basic telephone set. An analog TTE for the US market may use the recommendations of the Electronic Industries Association (EIA) 470-A, which encompasses telephone-handset transmission and receiving frequency response. The United Kingdom and Germany also have mandatory acoustic requirements for handsets, but those requirements differ greatly from EIA 470-A. Both countries have send-loudness-rating (SLR), receive-loudness-rating (RLR), and side-tone-masking-rating limits, which are a function of line length. The requirements thus dictate that you measure your equipment's performance at simulated line lengths. In the United Kingdom, British Standard (BS) 6317 specifies the limits as a series of curves. Tables 2a and b show the SLR and RLR limit curves for telephone handsets from BS 6317.

Germany plans to phase out FTZ 1 TR 2, a standard including acoustic requirements, by mid-1995. The country plans to replace the requirements with BABT 223 ZV5U, which offers substantially relaxed acoustic requirements. Section 2.8.1. 2 of BABT 223 ZV5U refers to the Committee on International Telephone and Telegraph's (CCITT's) Blue Book P series, P.64, P.65, and P.79 for performance and testing requirements. Thus, you must have this document if you intend to obtain approvals in Germany. And, if that is not confusing enough, a new addition, called DIN 44015 Parts 1 to 3, is on the horizon. This standard will be a recommendation but will not be mandatory.

Acoustic response is not the only attribute of the basic telephone that you must consider. Telephone-ringer impedance also poses hurdles. First, a universal design that meets every country's specifications does not exist. Second, the components you need for the impedance circuits vary considerably in size. Required capacitor values, for instance, range from 2 µF, 250V to 0.33 µF, 250V.

A simple, though not desirable, answer to this design problem is to rework the US design by changing capacitor and resistor values to meet the country's ringer-impedance requirements. You can hand-place the large capacitors as the rework is occurring. However, it can be difficult to find 250V surface-mount capacitors with large values, and they don't have the same footprint as smaller value capacitors. Thus, the unique approval requirements result in board and component changes sufficient to merit a different model number for each country-a nightmare if you have not thought about the problem early in the product-design cycle.

Some European requirements for a basic telephone have no equivalent in the United States. US telephones, for example, do not require pulse dialing, although vendors usually include this capability anyway. Pulse dialing is not in demand because of the widespread use of dual-tone multifrequency (DTMF) dialing, and FCC Part 68 does not test pulse dialing because its lack cannot harm the network. Europeans, however, make extensive use of pulse dialing, and most countries have performance requirements for it. The Swedish and German requirements for pulse dialing show how these requirements can conflict.

In Sweden, pulse-dialing circuits must include a spark squelch circuit with a capacitor >1 µF. The number of pulses (p) the phone sends to the central office must equal d+1, where d is the digit you dial. In Germany, the dial pulse shape must be sharp, having no capacitance, and the network performs dc-resistance measurements on the circuit during the pulse dialing. The pulse count a telephone sends when dialed in Germany must be p=d. You can resolve the digit/pulse difference in software, but the pulse-dialing circuit is tricky. You can also avoid the problem and ask your distributor in Sweden if you can get approval for and sell the product as DTMF-only.

Given the complexity European regulations add to ordinary telephones, expect products like data modems to require even more care. Proper handling of automatic-calling functions requires robust software. Fig 1 shows the required program flow for automatic calling, detailing the many steps in the automatic-calling sequence that any auto-calling analog TTE must follow. The calling sequence varies for voice and data equipment.

Initiating dialing and transmission in an auto-calling sequence can become complicated in some countries. If you want to sell products in Switzerland, for example, your equipment must detect busy tones with cadence on/off times as rapid as 120 msec on/180 msec off or 180 msec on/120 msec off. Frequency ranges for dial and busy tones range from 300 to 550 Hz. Other European countries have no-detect bands for lower and upper frequencies for call-progress tones. In Sweden, products must ignore dial-tone dropouts of less than 50 msec. If the dropout is greater than 100 msec, however, the TTE must not dial. For France,analog TTE must dial within 2 sec of application of dial tone.

As the variations indicate, TTE using call-progress ICs for the US market may not work properly. If the IC does not always dial within 2 sec, it does not meet the requirements for France. Although vendors can request waivers and restrictions, the goal is to pass the tests with a 100% grade. Consequently, beware of call-progress ICs that claim to meet European requirements: They may hit some requirements and miss others.

The challenges for telephones and data modems multiply for facsimile machines. A facsimile must meet all the requirements of the telephone set if it has a handset, a feature the market demands. Because facsimiles can provide automatic calling and answering, most of the requirements for data modems also apply. Facsimiles also have unique requirements, which come from CCITT Blue Book T Series, T.4 and T.30. Also, some countries add their own requirements.

France, for example, has stringent requirements. French testing labs run full CCITT transmit and receive tests on your products. However, the T.4 and T.30 protocols are open to interpretation. As a result, even if you design to the CCITT specifications, you may need to adjust your design unless you interpret the protocols in the same way as the French do. A facsimile machine may work and be compatible with other facsimile machines, but, if it does not handle faults and interrupts according to the CCITT recommendations, it will require more than one visit to the test lab in France. Austria and Germany also do T.4 and T.30 testing, although facsimile testing is optional in Germany.

Trying to obtain and meet all approval requirements for all countries is an enormous task, requiring that you focus your resources. Select your target countries and then obtain and sort all the approval requirements before formally including them in your design requirements. This approach helps to alert marketing to the task ahead for each country and to ensure that your product will succeed in the target countries.

You can adopt several strategies to ease your efforts at designing for widespread approval. One strategy is to group countries so that you can meet several countries' requirements with one test run. For example, the Scandinavian countries often share safety-test results and perform analog TTE testing for neighboring countries, reducing cost and saving time. Germany, Austria, and Switzerland also share some test requirements, as do the United Kingdom and the rest of the Commonwealth. Most of these countries either accept the test results of or have analog-interface requirements similar to those of other countries in the group. A UK configuration also may help you meet country testing in Singapore, Malaysia, South Africa, Kuwait, Australia, New Zealand, and India. France, on the other hand, is in a group by itself.

Your hardware design must anticipate the approval requirements that affect hardware. One approach is to allow for all possible changes by adding circuit traces that you may or may not populate and adding jumpers that set various parameters. This approach is possible if real estate is not an issue for the product. Because of the handwork involved, this approach works best at low production volumes.

Another approach, which suits higher production volumes, breaks the telephone circuit into two parts. A main board contains all the low-voltage and digital components, and a daughterboard holding the analog-telephone interface captures the country-specific interface requirements. The daughterboard isolates any missed requirements, making it easier and less expensive to make changes.

Software must also anticipate the requirements variety. The code you write must be flexible enough to allow for changes to timing parameters, call progress, signals from the PSTN or any other telephone parameters. Every telephony circuit should be software-programmable. Instead of writing large blocks of code that perform all the requirements for each country, however, use a runtime firmware matrix. This matrix lets you load a set of values based on country approval requirements into tables at initialization (see box, "The runtime firmware matrix"). The number of registers you need increases as you add countries to your target list or as you encounter new requirements. The resulting software, however, can approach a universal design.

Pretest your completed design for compliance before attempting to gain approval. Otherwise, your product most likely will fail approval tests, and you cannot nurse your design through the tests. You can pretest in your own lab if it has the required equipment, if you know the standards and test setups, and if you have the staff. A better approach, especially if you are trying to gain many countries' approvals at once, is to have a US-based European test lab perform the testing. This approach lets an engineer who is familiar with the European standards take a look at your product. In addition, making changes in a US lab is less costly and saves your reputation in European labs.

After you have acquired an approval certificate and are ready to ship your product, think about cables and labels. The cable you use for the telephone interface depends on the target country for the interface. The British connector must also have one end that attaches permanently to the telecommunications terminal-a condition of the safety approval. For other countries, ask your distributor how to handle the telephone cables. Sometimes, the distributor can open the boxes and replace the US cables with a country's required cables.

You must also use labels that show your product's approval for use in the target country. Generally, you purchase these labels from the country's approval body, as you do for equipment sold in Canada. Austria, Belgium, France, and Sweden are among the countries that provide labels, which you order after you receive the approval. For equipment sold in France, you must type the date of manufacture on the approval label before shipment. You must make your own labels for selling equipment to the United Kingdom and Germany. Because this requires some lead time, start early. Ask the Notified Body if it can release your product's approval number beforehand.

All these approaches offer only a glimpse of what it takes to sell a product in Western Europe. Negotiating your design through the approval maze is complex. There are no absolutes, and analog telecommunications approval is changing so rapidly that you must pay constant attention to it.