🚀 go-pugleaf

I am designing an ISDN S interface circuit.  It is intended for use mostly
on in-building wiring.  I am using the Siemens 2085.  I need some advice
on the protection circuitry required.  I currently am using 5.6V zener 
diodes on each leg. The transmit side has a 42 ohm resistor between the
diode and the chip.  The receive side has 10k ohm resistors between the
diodes and the chip. The transformer has a 2:1 turns ratio.

Is this sufficient?  Should the diodes be between the resistors and the
chip?  Is it better to use two regular diodes, one to vdd and one to vss,
rather than one zener diode?

All advice gratefully accepted.       
-- 
Joe Hingston            "A screaming comes across the sky"
Apple Computer, Inc.
(world!amdahl!apple!hingston)