3.4. CT Bus Timeslot Application Considerations

When multiple devices are listening to the same CT Bus timeslot, take into account the application considerations discussed in this section. Specifically, these considerations should be taken into account whenever a resource device (such as Voice, CSP, or other) listens to the same CT Bus timeslot device as a local, on-board Network Interface device (dtiBnTm).

NOTE:

There is NO restriction when listening to a CT Bus timeslot device to which the Network interface device is currently transmitting.

The following figure represents the cases discussed below.

Figure 1. Multiple Devices Listening to the Same CT Bus Timeslot

In a configuration where a DM3 network interface device shares (listens) the same CT Bus timeslot device with a local, on board voice (CSP, Fax, etc.) device, these considerations apply:

1. If an application called dt_listen( ) or gc_Listen( ) on a DM3 network interface device (dtiBwTz) to listen to an external CT Bus timeslot device (TS=120 in the figure), followed by one or more dx_listen( ), ec_listen( ), fx_listen( ), or other related functions to a local, on board voice device (dxxxBnCm) to listen to the same external CT Bus timeslot device, then the application MUST break (unlisten) the CT Bus voice connection(s) first, using dx_unlisten( ), ec_unlisten( ), or fx_unlisten( ), etc.), prior to calling dt_unlisten( ) or gc_Unlisten( ) to the local network interface device referred above. Failure to do so causes the latter call or subsequent voice calls to fail. This scenario could arise during recording (or transaction recording) of an external source, during a two party hair-pinning connection.
2. In the same scenario, if an application called dx_listen( ), ec_listen( ), or fx_listen( ), etc. first, then there is no particular sequencing order that must be followed during CT Bus timeslot device tear-down. However, full density (up to 120 channels) of CSP or Transaction Record might not be possible.
3. If multiple local, on-board network interface devices are all listening to the same external CT Bus timeslot device (in this case tslot = 120), the network interface devices must undo the CT Bus connections-that is, call dt_unlisten( ) or gc_Unlisten( )-so that the first network interface to listen to the CT Bus timeslot device is the last one to unlisten. This scenario could arise during broadcasting of an external source to several local network interface channels.

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