Juan Pedro Peqa wrote: > Doug: > At least in Spain, public switching telephonic network > works with 48 V dc but the ringing signal could reach > 75 V ac (hazardous voltage according to LVD). In fact, > if you catch both poles of a telephone line during the > ringing process, you will suffer that voltage. > So for that reason, LVD applies.
That equipment scenerio I perfectly understand. What you are describing is the ring voltage out to the subscriber from what's called here in the states an "end office". It's the last end of the trunk to the subscriber. This connection between an end office and the subscriber is called the "local loop". And typically the ring voltage is put out on the analog line to the subscriber. Ring voltages are NOT passed through the T1 or E1 trunk. In other words, the trunk between end offices or trunks between end offices and higher offices do NOT pass the ring voltage on the T1/E1 trunk. They cannot. It's not in the spec for T1 or E1. The ring *signals* are there, but not the ring *voltages*. So for equipment that connects to the local loop, I absolutely agree with you. Equipment outside the local loop, I do not. And again, I am not a supporter of this argument. It was a difficult one to get through. I am presenting it here merely to demonstrate the type of *speed bump* I've run into in compliance work. I'm showing what appears to be a good argument for a product that is outside EN60950 but in EN41003 and it speaks for some foresight on the part of our European neighbors if indeed I am right. I had to "go out of print" so to speak to undo someone that was hell bent on staying "in print". Safety cannot be written into a spec. Specs are nothing but guides. The engineer makes the call. And sometimes you must go out of spec to make such a call. Regards ************************************************************ ------------------------------------------------------------ The comments and opinions stated herein are mine alone, and do not reflect those of my employer. ------------------------------------------------------------ ************************************************************
