The voice signal can be routed to a plain old telephone service (POTS) provider or left unused whilst the data signal is routed to the ISP DSLAM via the HDF (see next entry). Handover distribution frame (HDF): a distribution frame that connects the last mile provider with the service provider's DSLAM DSLAM: a device for DSL service. The DSLAM port where the subscriber local loop is connected converts analog electrical signals to data traffic (upstream traffic for data upload) and data traffic to analog electrical signals (downstream for data download).