4 in 1 antenna adaptor

With Yeastar S-Series, all the telephony interfaces are modular and customizable, S100 allows 2 Expansion Boards to customize FXS, FXO, ISDN BRI, GSM/3G/4G, or E1/T1/PRI port. Yeastar IP PBX S100 – 100 Ext upgradeable to 200

With Yeastar S-Series, all the telephony interfaces are modular and customizable, S300 allow 3 Expansion Boards and Telephony Modules to add telephony interfaces.