Testing E1 Circuits
E1 circuit testing can be done with either of two methods: In Service and Out of Service
testing.
In Service testing is done during a routine maintenance and troubleshooting phase. This can
be accomplished without removing the E1 circuit from service on live data. Monitoring live
data allows the wireless service provider technician to detect alarms, bipolar violations
(BPV) and frame errors, but bit errors cannot be measured. However, bit errors may be esti-
mated by measuring CRC errors and E-bit errors.
Out of Service testing is done when the E1 is initially installed and before final acceptance
from the service provider. At that time the circuit should be subjected to critical testing to
guarantee the level of service per contract. Out of service testing may also be performed
when the circuit performance is very poor. For Out of service testing, the E1 circuit should
be removed from service to allow detailed performance testing.
In Service Testing
The Bridged mode must be used when testing a E1 circuit in service to avoid disrupting ser-
vice. Even when the E1 circuit is down, these tests will help to verify and identify the cor-
rect fault circuit. E-bits and CRC are very useful for in service testing to monitor E1
performance. When the equipment detects an incoming CRC-4 error, it will transmit an
E-bit error toward the equipment at other end which will be seen by the test unit. E-bits de-
termine the trouble location of the circuit. Without E-bits, the entire circuit will be deter-
mined as failure by loss of signal or alarm indication, so E-bits are critical to analyze the
performance of the circuit and point to the trouble locations.
The following measurements are used to check the E1 performance during regular mainte-
nance:
q
Vpp measurement
q
Carrier
q
Frame Sync
q
CRC errors and E-bits
Required Equipment
q
S331D Site Master with Option 50
q
Bantam Cables, Anritsu Part Number 806-16 (2)
Vpp Measurement Procedure
Step 1.
Press the
MODE
key, select
E1 Tester
, and press
ENTER
.
Step 2.
Select the
Vpp
soft key.
Step 3.
Press the
Terminate/Bridged
soft key and select
Bridged
mode, as indicated on
the bottom left of the status window.
Step 4.
Press the
75
W
or
120
W
soft key, depending on the requirements for the system
impedance value. The selection will be indicated at the bottom left of the status
window.
Chapter 8 E1 Measurements
8-3
