29. GDT for Telephone Line Lightning Protection

Aarav is designing a POTS (Plain Old Telephone Service) line interface for an industrial intercom system. 

The telephone line enters the building from outdoor overhead cabling, making it vulnerable to lightning-induced surges. 

He needs a Gas Discharge Tube (GDT) at the line entry point as primary surge protection. 

Key requirements: 

• The telephone line carries 48VDC on-hook plus ring signal up to 90Vrms superimposed, giving combined peak voltages up to 175V 

• GDT spark-over voltage: 230V (standard for POTS, above worst-case ring peak) 

• Surge current: ≥5kA (8/20µs) for lightning-class protection 

• 2-pole GDT (Tip and Ring in one package) 

• Surface mount package 

The company's AVL specifies Littelfuse, so the part must be selected from Littelfuse on DigiKey. 

Help him select a suitable GDT from Littelfuse on DigiKey.