An HDLC controller, essentially special-purpose circuitry on a motherboard, provides the ability to receive HDLC packets. For a full-duplex (FDX) SS7 link, 2 HDLC controllers are required.
TelcoBridges and HDLC
TelcoBridges supports HDLC via its Tmonitor family of products that support activities such as network monitoring, lawful intercept, and location-based services. The entry-level TM1000 device features up to 512 HDLC controllers, while the TM3000 devices support up to 2048 HDLC controllers.