On 8/14/2006, Jon Larkin wrote:
Can anyone tell me what the European voltage and current limits are for signals between a telephone handset and its PSTN-connected telephone? Hi Jon: I think your question needs to be a bit more specific in order for me to provide a useful answer. Are you concerned about safety compliance or are you trying to make use of these signals? For safety compliance, the answer depends on the internal design of the phone. Conventional, loop powered PSTN phones have no isolation barrier between the phone line and the handset, so the handset cord circuits will be classified as TNV-3 or possibly TNV-1 per EN 60950. On the other hand, most feature phones that use AC mains power have an isolation barrier that separates the phone line circuits from the (typically) SELV internal circuits including the handset. If the phone is used behind a PBX, the handset circuit can be TNV-1, TNV-2 or SELV, depending on the design of the PBX and the design of the phone. If your question is related to how you can use the handset connections, be careful. There is no standard interface for handsets, so each manufacturer uses whatever interface suits them for a given phone design. The currents, voltages, and even the pin assignments differ widely among various manufacturers and phone models. If the above does not answer your question please provide more details and I will try again. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) http://www.randolph-telecom.com <http://www.randolph-telecom.com/> ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
