Hello Vic, Thank you for the detailed reply.
1. I was really under the impression that a customer-premises system that is connected only to telephones and fax machines, etc., need not meet Part 68 or any European equivalent thereof, because there is no connection to the public network, and I was hoping to hear corroboration on that point. I based my assumption on the wording of the opening statement of Part 68: "The purpose of the rules and regulations in this part is to provide for uniform standards for the protection of the telephone network from harms caused by the connection of terminal equipment and associated wiring thereto, and for the compatibility of hearing aids and telephones so as to ensure that persons with hearing aids have reasonable access to the network." It seemed quite plain to me that if there is no connection to the PSTN, then no mandatory telecoms regulatory requirements apply, only voluntary ones. 2. Following on from the above, I wanted to check whether connection of such an internal system to the PSTN via an FCC Part 68 approved interface board (from Dialogic) would require the internal system to be separately telecom type approved, or telecom type approved in combination with the already approved Dialogic board. I wasn't worried about the safety aspects in this case because the Dialogic board would necessarily meet safety requirements. The only point that seemed problematic to me was voicebansd transmission level since presumably incorrect design could cause the approved Dialogic board to transmit at an excessive level. 3. The safety issues you mention are clear. I had been hoping that someone who has been through a similar design could have summarized the specific points to save my erroneous interpretation of EN60950/UL1950/CSA950. There are some tricky issues such as ringing voltages that do not fit the SELV category, and whether that affects the circuit design. 4. I was interested to hear that there is special provision for subscriber's equipment intended only for connection to a PBX extension. Where is this provision specified, and the labeling requirements, etc., described? Once again, thanks for your reply. David Drori
