Vic, Thank you for your reply which got buried in a huge number of received messages so that I only noticed it today!
Under normal conditions, the device isolates the fax machine from the PSTN. Under certain special conditions, the device connects the fax machine directly to the PSTN by means of an electromechanical relay that also disconnects all ground-referenced SELV circuitry that is connected to the fax machine at other times. It is quite clear that the device needs to fully address the different requirements of real-life fax machines in each of the countries of sale, including ringing frequency, voltage and cadence. As you say, NET4 provides a wealth of useful information in this respect. I have no concerns about the interface with the PSTN - we simply need to meet the relevant national requirements for non-voice equipment, and have a fair amount of experience in this area. However, I am still worried that the device will be officially classified as something other than a subscriber's non-voice terminal equipment, and be treated as a PBX, resulting in the need to meet regulatory requirements with respect to the fax machine connection, including requirements dictating functionality over longer loop lengths than we have in mind for this product, and a purer ringing waveform than the trapezoidal waveform (a la BELLCORE) that we plan. I suppose the 2-pole, 2-way electromechanical relay that switches the fax machine between (a) the PSTN outside line, and (b) the device's fax machine interface, including DC loop supply, ringing supply and loop detector, may also turn out to be problematic for a European design due to the stricter isolation requirements between the normally-open and normally-closed contacts. However, this doesn't sound like a problem that only we face, and I assume we will find something suitable. David Message text written by INTERNET:[email protected] >> 3. Will the regulatory authorities place this product in the category of a > PBX because it has at least one port to the PSTN and at least one port to > subscribers' equipment, even though the product's function differs from a > PBX and is only expected to operate correctly when the wire loop connecting > it to the subscriber's device is limited to several tens of metres? David, You do not tell us whether this device is an isolator between the public switched network and the faxmachine, or a switch-through device. Generaly speaking, in most countries the regulatory issue is whether the device has the capability to cause harm to the network (there are different views on what that means, in different countries). What you send from your device to the FAX machine is between you and the faxmachine manufacturer. Most "big name" faxmachine producers give you a range of options as to what the machine will respond to. Your device would only be evaluated on the characterisitics it presents to the network, not what characteristics it presents to the faxmachine. At home, I have a single telephone line, but two telephone numbers (on the same line). They each present a distinctive ringing signal. My fax machine responds only to one of those signals. H-P was kind enough to provide me with a number of choices. I feel confident, without checking, that they offer different choices in Europe, as will all the other big names. What used to be NET4 gave all the different possibilites in Europe. I haven't seen a late version, but if you can get your hands on an old version, you'll have a very useful document. It may not be a "standard" but it has most of the information you're looking for w.r.t. what different European telephone enterprises will do to you. My interpretation of the TTE Directive is that you need not worry about the regulatory aspects of the device - faxmachine interface (you certainly should from a marketing perspective). In North America, you'll have to worry about not putting outrages levels out to the fax machine, that would cause interference on adjacent lines. Ciao, Vic<
