1057 Called Directory Number Delivery via DID

This service allows the central office switch to deliver all or part of the
destination address to the ESP at the time the call is established.  Usually, 
the destination address delivered is the same as the number originally dialed.  
When number translations have occurred, e.g., 800 calls, the DID number
delivered is not the called number.

Generic Name of ONA Service
 	Product Name					BSE or CNS
===========================================================================
Called Directory Number Delivery via DID
	BA - Direct Inward Dialing Service		BSE
 	BS - Direct Inward Dialing			BSE 
        NX - DID					BSE or CNS
       	PB - Direct Inward Dialing To PBX Systems	BSE
       	USW - Called Directory Number Delivery (DID)	BSE

FEATURE OPERATION:
1. Customers order this service from the telephone company.  A client calling a
   customer is generally unaware that the customer has Direct Inward Dialing 
   (DID) service.  The client is not required to perform any additional actions
   to have the call delivered via a DID trunk group.

2. In a PBX type application, the service allows a client to reach a specific
   PBX station without the assistance of an attendant or other intermediary.

3. The number of digits forwarded by the central office switch is determined
   at the time the service is ordered.  The customer must also arrange for a 
   block of telephone numbers to be associated with the DID trunks.

TECHNOLOGICAL AND FEATURE INTERACTION CONSIDERATIONS:
1. This feature is available in the following central office switches:

Switch Type			1A ESS	5ESS	DMS-100
Earliest Generic Release	1AE8A	5E2(2)	BCS17

2. A customer may elect to receive Dial Pulse or Dual Tone Multifrequency
   (DTMF) signaling when using analog facilities.  If both the central office
   switch and the customer's equipment are digital, the customer may be able 
   to order DID trunks with digital connectivity.

3. This service is an incoming service (to the customer's CPE) and is
   typically a "trunk side" service.

4. References:
   o LSSGR (TR-TSY-000064), FSD 04-02-0000, Direct Inward Dialing,
     Issue 2, July 1987, Module TR-TSY-000524.

This service, if offered as a BSE, is associated with the Circuit Switched 
Trunk basic serving arrangement.
