1028 Automatic Protection Switching

Automatic Protection Switching provides the ability to monitor a non-switched
facility between the ESP premises and the wire center serving the premises and 
to automatically switch to a spare facility if the performance of the original 
facility degrades or fails.  It requires compatible equipment at both the ESP 
premises and the serving wire center.  

Generic Name of ONA Service
 	Product Name				BSE or CNS
===========================================================================
Automatic Protection Switching
	AM - Automatic Loop Transfer		BSE
	BA - Automatic Loop Transfer		BSE 
	BS - Automatic Protection Switching	BSE or CNS
	NX - Automatic Loop Transfer		BSE or CNS
	PB - Automatic Loop Transfer		BSE
	PB - Digital Data Service		BSE
	SWB - Automatic Loop Transfer		BSE 
	USW - Automatic Loop Transfer		BSE

FEATURE OPERATION:
Automatic Protection Switching (APS) can be offered in two configurations.  
It can be offered as a stand alone APS for use with T1 carrier or as DS1 APS 
incorporated into a DS3/1 multiplexer unit.

The stand alone unit, in conjunction with an identical unit at the opposite end
of the T1 carrier facility to be protected, switches from the primary T1 carrier
facility to a standby facility upon detection of a loss of the 1.544 Mbps signal
or of an unacceptable Bit Error rate.  There are two T1/1.544 Mbps inputs from 
the line side of the unit, a primary input and the standby input.  The inputs 
normally terminate on a cross connect device and are connected to the DS1 Access
Link carrier facilities between the Serving Wire Center and the Customer 
Premises.

There is one 1.544 Mbps output port on the APS unit.  In the central office
it will be terminated on a digital cross connect frame for interconnection
with other DS1 facility terminations or switch appearances.  On a customer
premises, it will be terminated on a standard Network Interface.

The DS1 APS method is accomplished by means of circuitry contained within the 
DS3/1 multiplexer.  The low speed DS1 cards can have an optional APS capability
on a DS3 basis.  Some levels of protection are 1 for 4 and 1 for 7, depending 
upon the manufacturer of the multiplexer unit.  This equipment is part of a DS3
or higher level transmission system and can not be applied to metallic-based 
T1 carrier.  The facility side DS1 is internal to the multiplexer.  The DS1 
output of the multiplexer is terminated on a DS1 cross connect frame in the 
Serving Wire Center. 

TECHNOLOGICAL AND FEATURE INTERACTION CONSIDERATIONS:
1. This capability must be deployed on a circuit by circuit basis when
   offered in a stand alone configuration.

2. There is no feature interaction.

3. References:
   o OTGR: Network Maintenance: NE, TR-TSY-000474
   o Specification of System Maintenance Messages at the OS/NE Interface,
     TA-TSY-000200
   o DS1 AFPS For Digital Terminal System, TA-TSY-000435
   o Digital Radio System TA-TSY-000238
   o SONET Requirements, TA-TSY-000755

This service, if offered as a BSE, may be associated with the Dedicated Digital
(< 64 kbps), Dedicated High Capacity Digital (1.544 Mbps) and Dedicated High
Capacity Digital (> 1.544 Mbps) basic serving arrangements.
