>There are strick requirements for the routing and spacing for the tip and
ring per UL.
>
>Scott Buscomb
>Techsonic Industries Inc.
>
>Paul Brionez wrote:
>
>> I am currently working on a design that includes an on-board modem. Does
>> anyone know of any requirements on a national or international standard
as
>> to the design requirements. The circuit is pretty straight forward with
>> isolation and Tip & Ring. I am wondering is there any additional
>> restrictions as they are applied to this type of circuitry. Thanks in
>> advance for the assistance.


Yes, and you should consider an isolation of 4kV or at least 2.5 kV. I'm
using 100mils of isolation on these traces and the result is pretty good, no
sparks. The boards are FCC and UL approved. Also, if the board is
multilayer, it should not have a copper plane over this part of the circuit
(usually up to the transformer).

Rgds,

Paulo Egon

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