All Zero Framed: F00000000

The All Zeros pattern is effective in verifying correct optioning for a B8ZS transmission line. The ALL Zeros signal is converted to 00011011 if one or more repeaters in the transmission line are optioned for AMI. The All Zeros signal remains 00000000 if all the repeaters in the transmission line are optioned for B8ZS.

QRSS Framed: Quasi-Random Signal Source

The QRSS pattern simulates a T-1 circuit carrying voice signals. The pattern generates every possible sequence of 20 bits and generates a broad frequency spectrum. Transmitted as framed, QRSS contains 15 consecutive zeros; unframed contains 14 consecutive zeros. The QRSS pattern tests both the timing recovery and equalization circuitry of a repeater.

The timing circuitry is stressed by the low ones density sequences. The equalization circuitry is also stressed by the broad frequency spectrum of the sequences. If the circuitry passes these stress patterns, other tests are required to isolate faults.

2 In 8 Framed: F01000010

The 2 in 8 pattern determines if the transmission equipment is improperly optioned for B8ZS. This pattern finds misoptioned equipment but does not invoke the B8ZS sequence, since eight consecutive zeros are required for the substitution. This pattern is also designated as 2:6.

1 in 8 Framed: F010000000

The 1 in 8 pattern stress tests the facilities. When this pattern is sent framed, the B8ZS sequence occurs on the zero framing bit, which increases the ones density. When error occurs, the circuit can be intolerant to low-density patterns. This pattern is also known as 1:7.

All Ones Frames: F11111111

The All Ones pattern stresses the repeaters in the transmission facilities to consume the maximum amount of power. When the DC voltage to the repeaters is regulated correctly, the repeaters have no problem transmitting long ones sequences.

Acceptance Testing for B8ZS ESF Circuit

Test Pattern	Test Duration
Framed All Zeros	Go/No Go*
2 in 8	Go/No Go*
QRSS	30 Minutes
1 in 8	10 minutes
All Ones	5 minutes

*Acquiring synchronization with the ability to send and receive bit errors without any unaccounted for errors constitutes a Go on framed All Zeros and the 2 in 8 patterns.