Unit installation

Chapter 6 Troubleshooting and Diagnostics FCD-E1 Installation and Operation Manual
6-22 Testing FCD-E1
Channel Inband Loopback (LP INBAND CH)
FCD-E1 supports both reception and transmission of the inband-activated
loopback, in accordance with the ANSI FT1/FE1 RDL (T1E1.2/93-003).
The inband-activated channel loopback can be performed using two sites, Site A
(transmitter) and Site B (reciever), and is similar to the data channel remote
loopback, except that it is performed on the Site B FCD-E1, in response to a
command entered at the Site A FCD-E1. The loopback is performed towards the
Site A local user’s equipment connected to the data channel.
The remote loopback is activated and deactivated by transmitting special
sequences for approximately 2 seconds from Site A unit causing it to enter the
TX INBAND state.
When an inband loopback pattern is sent by the Site A equipment (connected to
the main link of the Site B unit), and the Site B equipment BERT detects this
pattern for approximately 2 seconds, a remote loop is initiated on the data channel
of the Site B unit, causing it to enter the RX INBAND state. Once the remote data
channel loopback is on, the Site B unit BERT tries to match loop deactivation
series.
To enable the activation of a remote loopback in response to the reception of the
inband loopback command from the remote system you must activate the DEF
BERT CH command and set the RX_INBAND parameter to ENABLE.
BER Testing (LP BERT CH)
BER testing can be performed on one channel at a time. To perform the test over
the whole link, end-to-end, use the inband activated loopback; for a local test, use
one of the local main link loopbacks, or any other loopback that returns the data
towards the local DTE, must be activated.
During the test, the local DTE is disconnected and the DSR line is off; an internal
pattern generator connects a user-selected test sequence to the transmit input of
the local data channel interface. To calibrate the system, the user can inject errors
at a selectable rate.
The receive output is connected to a pattern evaluator. The evaluator compares
the received and transmitted patterns and detects errors. The test results are
presented as follows:
• On the supervision terminal, detailed full data is displayed, including
information on factors such as the number of seconds during which the
FCD-E1 lost frame synchronization (see the DSP BERT command in
Appendix D).
• On the LCD, the result appears as GOOD (no errors) or BAD (at least one
error has been detected during the BER measurement interval).
Note