Roger, There are a couple of specifications that I reference quite often for exactly this type of question. The specifications are as follows: * ANSI T1.401-1993; Interface between Carriers and Customer Installations - Analog Voicegrade Switched Access Lines Using Loop-Start and Ground- Start Signaling. * TIA/EIA-464-B; Requirements for Private Branch Exchange (PBX) Switching Equipment. In my experience, setting the DTMF levels at -8 / -10 dBm @600 ohms will not affect a products ability to access the network correctly and consistently.
Regards, Daren E. Allen CPCG, Displays and Peripherals Division Connectivity Business Unit *Voice: 281-518-0881; *Fax: 281-927-9433; *Pager: 713-710-0093 *Email: [email protected] <mailto:[email protected]> -----Original Message----- From: Roger Magnuson [mailto:[email protected]] Sent: Monday, September 27, 1999 8:58 AM To: TREG Subject: DTMF in USA Importance: High Hello TREGgers, According to FCC Part 68, 68.308(b)(2)(i)(A), the maximum limit for the DTMF signal power level is 0 dBm. We found that a majority of modems (at least those based on Conexant...) use a DTMF level of -4/-6 dBm for the US market. These sending levels are difficult to achieve these days (mainly "thanks to" 3.3V modem devices and high insertion loss of line transformers suitable for 56K). Now, to avoid the painful trial and error method I'd like to know if there is any published specification (Bellcore?) that defines a recommended power level for DTMF signals in the US? In your experience, would equipment with -8/-10 dBm power level operate correctly? Thanks for your help..... Roger Magnuson Manager, Marketing & Business Development TGC AB Dalvagen 28, 169 56 SOLNA, Sweden TEL: +46 856250050 (direct) FAX: +46 856250045 (NOTE our new fax number) mobile: +46 707770594 mailto:[email protected] internet: http://www.tgc.se
