Typical Application of a HandyTone-496:

Comprehensive
HandyTone Series comparison table:

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FXO port allows local and remote PSTN-to-VoIP call origination
and VoIP-to-PSTN call termination, automated call routing
through PSTN, and power fail-over. PSTN Pass-through allows
local PSTN line service for income/outbound call and failover.