In a message dated 96-05-09, George Seminsky writes: > We are investigating analog telco interface circuits, in particular SLICs, > with a goal of defining a single or a minimum number of designs which can > meet the NET 4 requirements of at least the following countries in the EU: > Germany, UK, France, Italy, Switzerland, Spain. We are currently looking >at the Mitel MH88600 for these applications. The applications engineer at > Mitel has indicated that the device can be programmed to required line > impedance of any EU country but does not have, at this time, information of > other country-specific telco performance requirements that must be met. > Have any of you been through a similar process and are able to provide > suggestions as to where to look and how to proceed?
George: Oh boy, this question does not lend itself to a simple answer. However, I can make the following observations: 1) NET 4 specifies the requirements that several European countries place on PSTN terminal equipment. Terminal equipment (such as a phone or modem) is intended to be on the receiving end of the central office or PBX feed circuit. If you are designing a SLIC (the central office or PBX feed circuit), NET 4 will be of little use. At best, you can gather some descriptive information about the various PSTN networks in Europe by reviewing chapter 1 of NET 4. 2) The closest thing that Europe has to a harmonized specification for SLIC circuits appears in the ETSI document I-ETS 300 004, "Transmission Characteristics at 2-Wire Analogue Interfaces of a Digital Private Automatic Branch Exchange" dated August 1991. This document is somewhat out of date, and it contains several requirements that are quite difficult to meet (especially those related to trans-hybrid loss). Fortunately, most European countries do not use this standard, although Switzerland's national standard for PBX's (SR 784.103.12/4.1/1) specifically references several subsections of this standard. 3) It is my impression that the Mitel MH886XX series of devices were designed primarily for the North American market. Depending on which member of this family you choose, the designers have made varying degrees of efforts to make provisions for international compliance. However, it appears that in most cases, their efforts were only a "best guess", and it is essentially up to the user to prove in the part for a specific international requirement. I have had two clients who used devices from this family to implement the TE interface on a PBX. In both cases, I got involved when they failed to meet certain international requirements. In both cases, Mitel had to make changes to their design to fix the problems. In the case of a SLIC circuit such as the MH88600, you might have better success. This is because Mitel uses a very non-traditional method for implementing their TE interfaces, but they use a more traditional method for implementing their SLICs. However, I have not actually used the MH88600 in a product design, so I can not vouch for its suitability. 4) If you want to implement a SLIC circuit that is easily configured for multiple countries, I would suggest coupling a relatively simple SLIC with a programmable codec such as the Siemens PEB 2260 or the AMD 79C02. This gives you software configurability of gain, frequency response, return loss and transhybrid loss. The only penalty is higher cost. 5) For the SLIC itself, you could consider the Harris 5509A1, which I have used successfully in Switzerland. On the other hand, Mitel told me last year that they were working on a new, simplified SLIC that was specifically designed to be paired with the Siemens PEB 2260 programmable codec. Perhaps this part is available now. 6) Lastly, it occurs to me that you may actually have intended to ask about configurable PSTN TE interfaces, since you did mention NET 4, despite the fact that you also mentioned SLICs and the Mitel MH88600. If your true interest is actually TE interfaces, please disregard all of the above. For TE interfaces, NET 4 is an excellent starting point, and you can accomodate all of the countries that you listed with only a few configurable parameters. However, your best approach is to design your own interface circuit, rather than purchasing a ready-made module. If it turns out that this is, in fact, your area of interest, give me a call and I will give you my two cents on that subject! Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 617-721-2848
