Black Box 34336 User Manual

The RX value is the local receive level of the incoming signal. The receive
level range of measurement is from 0 to  -43 dBm in 1.5-dBm increments.
If the signal level is less than the carrier detect threshold, "<CD" is
displayed.

•  Echo Characteristics Screen. Displays the characteristics of the echo

portion of the receive signal. Specifically, it shows milliseconds of delay
and the offset frequency in Hertz.

•  Channel Frequency Offset. Displays the frequency offset of the receive

signal in Hertz.

•  Throughput Screen. Functions only if error correction is  enabled.

It shows the rate (in bits per second) at which the Modem is accepting
charatcters from the DTE.

•  Packet Screen. The packet screen functions only when error correction

is enabled. It has three components, as explained below.

Size. Shows size of data packets (MNP) or blocks (V.42/V.42 bis)
currently being transmitted. MNP uses shorter packets to transmit
through noisy lines and longer packets (allowing greater throughput)
when line conditions are good. The maximum MNP packet size is 64
(MNP classes 1-3) or 256 characters (MNP classes 4 and 5). The block
size for V.42/V.42 bis is fixed at 128 characters.

Transmitted (TX). Number of packets or blocks transmitted since the
connection was established.

Errors (ER). Number of retransmissions (retransmitted because of data
errors) since the connection was established.

•  Mode and Rate Screen. Shows the following data:

Mode. Below MODE, the screen indicates the error correction status:

NORMAL — Error correction and buffer mode are both inactive.

V42 — V.42 error correction (LAPM) is active.  

V42bis — V.42 bis error correction (LAPM with data compression)
is active.

MNP 01 to MNP 05 — MNP error correction is active.

BUFFER — Buffer mode is active.

OFFLINE — Modem is off-line.

Rate.  Shows the data rate of the DTE.