What type of phone lines does Crux work with?

Crux can work with PSTN (also referred as POTS or DEL or Phonenet or Analog Landlines), ISDN (also referred as PRI/E1/J1/T1), SIP Trunk (also referred as multi-channel Digital Landline), as well as GSM SIM (2G/3G/4G but with non-VoLTE voice) cards.

Since SIP trunks are IP-based technology, it can natively (or directly) connect to Crux without requiring any conversion. For the rest of the types of phone lines, an additional HSPA modem (for GSM) or an ATA / ISDN gateway (for PSTN or ISDN) is used to do the conversion to work reliably.