Type-1 NSA ACC-compliant gateway using the GD Sectéra® vIPer™ Secure Phone. The Secure Device Interface (SDI) circuit card enables the REDCOM HDX to interface with up to four standard production General Dynamics Sectéra® vIPer™ devices, which act as voice encryptors for TDM or SIP voice networks. The encryptors allow any HDX line, trunk, or conference port to conduct secure voice communications with any SCIP-capable device. The HDX supports up to 64 SDI ports per 5U modular switching unit (MSU). HDX MSUs may be stacked to allow for hundreds of SDI ports per system.