Protection-matching Transformers
Protection-matching transformer has two basic functions: galvanic separation between device and telephone line and adjustment device impedance to the characteristic telephone line impedance.
Regarding impedance transmission ratio there are 4 types of transformers:
- 600:600 Ω, Tm 1702-N42
- 1200:1200 Ω, Tm 1702-N14
- 600:1200 Ω, Tm 1702-N42
- 2000:5000 Ω, Tm 1702-4173
Loading (Pupin) Coil KP Tm 602-80
Loading coil has inductivity of 2x80mH and is used for loading of underground cable lines. Coil is used to correct amplitude distortions that are result of unequal attenuation of line signals at the different frequencies. Loading coil placed along the line gives uniform attenuation in AF range. Two telephone pairs can simultaneously be loaded by one coil.