Equations to calculate different value attenuations

---R1---+---R2---
|
-> Z1 R3 Z2 ->
|
---R1---+---R2---


R1 = ((Z1 + Z2)* 0.994 + (Z1 - Z2))/4

R2 = ((Z1 + Z2)* 0.994 - (Z1 - Z2))/4

R3 = (Z1 + Z2) / attenuation

Example: Z1=600 ohms Z2=600 ohms attenuation=317.3 (=50 dB)
Then R1=298 ohms, R2=298 ohms, R3=3.78 ohms