# Setting or retrieving the echo cancellation bypass state

The bypass control allows you to enable or disable the hardware echo cancellation feature for a trunk port. Use swiConfigLocalTimeslot to set the echo canceler bypass state and swiGetLocalTimeslotInfo to retrieve the echo canceler bypass state. Set the arguments for these functions as follows:

Argument | Field | Value
swihd |  | Handle returned by swiOpenSwitch.
args | localstream | Identifies the target trunk on the local bus. Specify the number of either the transmit or receive voice stream. Refer to CG 6565 switch models for more information.
localtimeslot | Identifies the target timeslot on the trunk. Specify the timeslot number of the target trunk port on the local bus. Refer to CG 6565 switch models for more information.
deviceid | Device type on the local bus. The deviceid is hardware dependent. For example, MVIP95_T1_TRUNK_DEVICE or MVIP95_E1_TRUNK_DEVICE. For information about the deviceid, refer to the Dialogic® NaturalAccess™ Point-to-Point Switching API Developer's Manual.
parameterid | Data item to configure or query. Set to NMS_ECHO_CHANNEL_BYPASS (0x80000007).
buffer |  | Points to the NMS_ECHO_CHANNEL_BYPASS_PARMS structure. Valid values are: 0 = NMS_ECHO_BYPASS_DISABLE 1 = NMS_ECHO_BYPASS_ENABLE
size |  | Size of buffer, in bytes.

The NMS_ECHO_CHANNEL_BYPASS_PARMS structure is:

typedef struct
{
DWORD bypass; /* NMS_ECHO_BYPASS_DISABLE or NMS_ECHO_BYPASS_ENABLE */
} NMS_ECHO_CHANNEL_BYPASS_PARMS;

The value returned from the NMS_ECHO_CHANNEL_BYPASS_PARMS structure indicates whether the echo cancellation bypass state is enabled or disabled for the specified device.

For information about the echo cancellation bypass feature, refer to Using echo cancellation control. For more information about swiConfigLocalTimeslot or swiGetLocalTimeslotInfo, refer to the Dialogic® NaturalAccess™ Point-to-Point Switching API Developer's Manual.

## Setting the bypass state example

The following example shows how to set the echo canceler bypass state:

#include "swidef.h" /* Switching service */
#include "mvip95.h" /* MVIP-95 definitions */
#include "nmshw.h" /* Hardware-specific definitions */
DWORD mySetBypass(SWIHD swihd, SWI_TERMINUS terminus, int bBypassEnabled)
{
SWI_LOCALTIMESLOT_ARGS args;
NMS_ECHO_CHANNEL_BYPASS_PARMS parms;
args.localstream = terminus.stream; /* from board switch model */
args.localtimeslot = terminus.timeslot; /* from board switch model */
args.deviceid = MVIP95_T1_TRUNK_DEVICE; /* mvip95.h */
args.parameterid = NMS_ECHO_CHANNEL_BYPASS; /* nmshw.h */
if (bBypassEnabled)
parms.bypass = NMS_ECHO_BYPASS_ENABLE; /* nmshw.h */
else
parms.bypass = NMS_ECHO_BYPASS_DISABLE; /* nmshw.h */
return swiConfigLocalTimeslot (
swihd, /* switch handle */
& args, /* target device and config item */
(void*) & parms, /* buffer (defined by parameterid) */
sizeof(parms)); /* buffer size in bytes */
}

## Retrieving the bypass state example

The following example shows how to retrieve the echo canceler bypass state:

#include "swidef.h" /* Switching service */
#include "mvip95.h" /* MVIP-95 definitions */
#include "nmshw.h" /* Hardware-specific definitions */
DWORD myGetBypass(SWIHD swihd, SWI_TERMINUS terminus, int* pbBypassEnabled)
{
SWI_LOCALTIMESLOT_ARGS args;
NMS_ECHO_CHANNEL_BYPASS_PARMS parms;
DWORD swi = SWI_SUCCESS;
args.localstream = terminus.stream; /* from board switch model */
args.localtimeslot = terminus.timeslot; /* from board switch model */
args.deviceid = MVIP95_T1_TRUNK_DEVICE; /* mvip95.h */
args.parameterid = NMS_ECHO_CHANNEL_BYPASS; /* nmshw.h */
swi = swiGetLocalTimeslotInfo (
swihd, /* switch handle */
& args, /* target device and config item */
(void*) & parms, /* buffer (defined by parameterid) */
sizeof(parms)); /* buffer size in bytes */
if (parms.bypass == NMS_ECHO_BYPASS_ENABLE) /* nmshw.h */
*pbBypassEnabled = 1; // true
else
*pbBypassEnabled = 0; // false
return swi;
}