Zycoo IP PBX without module, Extension Users:200, Concurrent Calls:80(Max), Supported Module:4FXS/4FXO /2FXOS/ 2GSM/4GSM/2WCDMA/ 4WCDMA, Supported Maximum Module : 2 ,Voicemail/Recording:15000Hrs (internal storage) SDRAM: 1GB DDR3, Storage:8G SD Card (Industrial grade)+ 1TB Surveillance HDD