Mel,
probably your customer referes to the German Advisory Note DE 09 of ETSI Guide EG 201 121. This note states that proper interworking with the German PSTN only can be guaranteed when the return loss during the transmission of DTMF signals is greater than 14dB. Most designs today don't change their impedance during dialling. So this is a general requirement for the loop state. Looks like choices 1) and 2) of your request apply. ;-) Regards ______________________________________________________________ [] Karl-Heinz Doerfler Director Engineering Quality Assurance | ELSA AG Phone: +49 241 606 2271 | Sonnenweg 11 Fax: +49 241 606 2099 | D-52070 Aachen EMail: [email protected] ______________________________________________________________
