Out‑of‑service measurements are performed when the T1 circuit is not in-service or is inactive. Typically, these tests are done during initial installation, during circuit acceptance by the wireless service provider, or when the performance of the circuit is below acceptable levels.
Two methods of performing out‑of‑service testing are: end‑to‑end and loopback testing. End‑to‑end testing requires a technician and a unit at each end of the circuit. Loopback testing requires a loopback at one end of the circuit and a unit and technician at the other end to measure the round trip BER of the T1 circuit.
The ANSI T1 standard defines in‑band and out‑of‑band loop codes. In‑band codes are transmitted in place of payload data and are repeated continuously for a period of five seconds. They can be used either with SF D4 or ESF. Out‑of‑band loop codes can be used only with the ESF framing format, because an out‑of‑band communication link does not exist for SF D4.
The following measurements can be used to check T1 performance during out-of-service testing:
• Vpp
• Carrier
• Frame Sync
• CRC Errors, for Extended Super Frame (ESF)
• BPV
• BER
• Frequency
Required Equipment
• Bantam Cables, Anritsu Part Number 806‑16 (2 cables required)
Measurement Setup Procedure
1. Press the Configuration main menu key.
2. Use the Up/Down arrow keys or the rotary knob to highlight Line Code and press the B8ZS or AMI coding submenu key.
3. Select one of the three Tx Clock types: Internal, Recovered, or External.
4. Use the Up/Down arrow keys or the rotary knob to highlight Tx LBO and select either the 0 dB, – 7.5 dB, or – 15 dB transmitter signal level submenu key as appropriate to the measurement.
5. Use the Up/Down arrow keys or the rotary knob to highlight Rx Input and press the Terminate submenu key.
6. Use the Up/Down arrow keys or the rotary knob to highlight Framing and press the ESF or SF‑D4 submenu key as appropriate for the measurement.
7. Press the Pattern/Loop main menu key to activate the pattern and loop code menu.
8. Press the Select Pattern submenu key, use the Up/Down arrow keys, or use the rotary knob to highlight the appropriate pattern, and press the Select Pattern submenu key or press Enter. The selected pattern can be reversed (only supported for PRBS patterns) by pressing the Inverse Pattern submenu key.
Note
Up to six user‑defined patterns can be created by pressing the Set User Pattern submenu key and pressing the User‑Pat 1 through User‑Pat 6 submenu keys. Use the Up/Down arrow keys, rotary knob, or key pad to enter the desired pattern. Table: Defined Test Patterns summarizes the T1 patterns that are available in the instrument.
9. Connect the Tx and Rx ports to the circuit under test.
10. Verify carrier and frame sync before proceeding.