Yeastar SO Module (1 FXS + 1 FXO)

The GSM module is a module with 1 GSM channel that couldcall out by GSM
Unique PSTN Fall back Function, Make/receive call, when system powers down.

Yeastar SO Module – Specifications

Ports & Compatibility

• Ports: 1 × FXS (RJ‑11), 1 × FXO (RJ‑11)

• Compatible with Yeastar S‑Series PBX (S20, S50, S100, S300) and P‑Series PBX (P550, P560, P570)

Telephony / Line Support & Functionality

• Supports connection of one analog phone/fax (via FXS)

• Supports one PSTN line (via FXO) for trunk or external line connection

• Provides PSTN fallback: in case of PBX system failure or power outage, phone connected to FXS can still ring / use the PSTN line connected via FXO — ensuring call continuity

• Supports analog devices (phone, fax, analog lines)

Signalling / Line Characteristics

• FXO port ring-frequency detection: 15–50 Hz

• FXS port ring-frequency: 25 Hz

• Ring voltage: 85 V

• Termination impedance option: 600 Ω

• Built-in echo cancellation

Use Cases & Advantages

• Allows hybrid PBX setup: mix of VoIP and analog/PSTN lines/devices

• Good for small offices needing an analog phone plus PSTN trunk via a single module

• Handy as failover/back‑up branch: analog line remains usable if main PBX fails