# Using echo cancellation control

The CG 6565E board includes a hardware echo cancellation feature that offloads DSP processing time for running other functions. The hardware echo canceler is located between the switch and the trunking framers, placing the echo canceler feature at the trunks. The control API allows you to modify hardware echo cancellation features for a trunk port.

Applications can query and configure features of the hardware echo cancellation feature on a per-timeslot basis. Because the echo chip is wired in series between the switch and trunking framers, specifying the MVIP address of the associated trunk port identifies the individual echo cancellation channels. Refer to the CG 6565E switch models for your board, to identify the MVIP address.

Echo cancellation control uses the Switching service for configuring and querying the board-specific hardware parameters. swiConfigLocalTimeslot and swiGetLocalTimeslotInfo allow applications to configure or query a device on a given local stream and timeslot by specifying a particular parameter and providing a data structure specific to that parameter. The syntax for these functions is repeated here for your convenience.

Refer to the Dialogic® NaturalAccess™ Switching Interface API Developer's Manual for details about the Switching API.

## Syntax

The syntax of swiConfigLocalTimeslot and swiConfigLocalTimeslotInfo is:

DWORD swiConfigLocalTimeslo t ( SWIHD swihd, SWI_LOCALTIMESLOT_ARGS *args, void *buffer, unsigned size )

DWORD swiGetLocalTimeslotInfo ( SWIHD swihd, SWI_LOCALTIMESLOT_ARGS *args, void *buffer, unsigned size )

Argument | Description
swihd | Switch handle.
args | Pointer to a SWI_LOCALTIMESLOT_ARGS structure. This structure indicates the specific parameter to be configured or queried on the device indicated by localstream and localtimeslot. typedef struct { DWORD localstream; DWORD localtimeslot; DWORD deviceid; DWORD parameterid; } SWI_LOCALTIMESLOT_ARGS;
buffer | Pointer to a structure that is specific to the parameterid.
size | Size of buffer, in bytes.