In a message dated 97-07-23, Feliz Eryilmaz writes: << Is or will a ringer equivalent of zero be acceptable in European Countries?Some countries specify a ringer capacitance between 0.33 and 1.0 uf. >>
Feliz: In the past, some of the countries that specified a minimum capacitance were Belgium, Czech Republic, Germany, Greece, Ireland, Italy, Korea, Malaysia, and South Africa. Germany has also specified a maximum impedance magnitude (20 K ohms). These requirements were generally derived from the characteristics of existing analog phones, and were sometimes defended on the basis that automated line testing equipment relied on a known termination. Over the past few years, many of these countries have dropped the requirements or relaxed their enforcement. In Europe, there is pressure from prTBR 21, which imposes no minimum capacitance or minimum impedance. For instance, I believe that Ireland now requires only a minimum of 8 K ohms impedance. If and when CTR 21 appears in Europe, there is likely to be no minimum requirement on capacitance or maximum requirement on impedance throughout Europe. So, if you wish to implement a design with an "infinite" ringer impedance, the overall trend in the industry is in your favor. However, you will have to carefully review the current situation in each of the above named countries before you proceed. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc.
