The configuration is accessed by pressing the Configuration main menu key. This menu is used to configure the Signal Setup and Payload Setup. The Signal Setup allows the user to set up the Line Code, Tx Clock, Input Connector, Rx Input, and Framing information. The Payload Setup allows the user to set up the payload type and payload channels for payload types other than 2.048 Mb.

Submenu keys for the Configuration menu are shown and described in section Configuration Menu and in Figure: E1 Configuration Submenu Keys.

E1 ‑ 2 Mb/s is a 2.048 Mb/s signal consisting of 32 individual timeslots. Each timeslot has individual 64 kb/s channels of data.

Alternate Mark Inversion (AMI) and High Density Bipolar 3 (HDB3) are two different line coding formats used in E1 ‑ 2 Mb/s networks.

In the AMI format, a binary one is represented by a pulse, and a zero is indicated by the lack of a pulse. To eliminate any DC offset, the pulses alternate in polarity. Because the pulses are alternating in polarity, the line code is called Alternate Mark Inversion (AMI). If two consecutive pulses have the same polarity, then a Bipolar Violation (BPV) has occurred.

When no traffic is present on a channel, AMI coding can result in long strings of zeros on the circuit. This can cause the receiving equipment to have timing errors. HDB3 is a line coding format which also has no DC offset, but which replaces strings of 4 or more zeros with a specific code containing a BPV. The next HDB3 insertion uses the opposite polarity to maintain a net zero DC offset on the circuit. The HDB3 code is detected and removed by the receiving equipment.

Internal Clock: Use the internal clock oscillator (2.048 MHz ± 5ppm)

Recovered Clock: The transmit clock uses the frequency recovered from the received signal.

External Clock: The transmit clocks uses the external clock that is applied to the External Trigger In connection.

RJ48, 120 Ω: Uses the 120 ohm RJ48 connector.

RJ48, 75 Ω: Uses the 75 ohm RJ48 connector.

BNC, 75 Ω: Uses the 75 ohm BNC connector (Option 52 only).

Terminate: The signal is terminated in 120 ohms or 75 ohms depending on selected Input Connector.

Monitor: The connection to the circuit is made through a monitor jack. The jack is isolated from the circuit with resistors, and the signal is typically 20 dB down from the nominal signal level. When Monitor is selected, 20 dB of flat gain is added at the receiver input.

Bridge: The input impedance of the receiver is greater than 1000 ohms. The bridged mode is used when connecting directly to an in-service E1 ‑ 2 Mb/s circuit to avoid causing a “hit” on the signal and to avoid disrupting service.

If an E1 ‑ 2 Mb/s SETS (Synchronous Equipment Timing Source) reference clock is available, then it can be used to measure clock slips and frame slips on the circuit under test. If two or more E1 ‑ 2 Mb/s circuits are present, then one of these can be used as a reference.

To count clock slips, connect the reference clock to the Ext Trigger In connector on the instrument. The presence of the clock is automatically detected, and when a measurement is started, the number of clock slips and frame slips are reported. When the clock frequencies are very close, the clock slip count will hover around zero. If the frequency of the circuit under test is higher than the reference frequency, then the count will grow positive. If the frequency of the circuit under test is lower than the reference frequency, then the count will grow negative. One frame slip is counted for 256 clock slips.

PCM30: 30 voice or data channels, TS16 is used for CAS, no CRC‑4 multiframe.

PCM30 CRC: 30 voice or data channels, TS16 is used for CAS, with CRC‑4 multiframe.

PCM31: 31 voice or data channels, no CRC‑4 multiframe.

PCM31 CRC: 31 voice or data channels, with CRC‑4 multiframe.

The Payload identifies which portion of the 2 Mb/s data stream will be accessed for testing.