User`s manual

EAGLE
Multi-Standard Dual-Channel Digital Audio Codec
17
4.3. Default startup.
The equipment needs prior configuration of certain parameters in voice calls (G.711) and links
at 128 kbps, in order to be compatible with other units, as well as, to meet certain requirements
of the user. These configurations will be active as soon as the unit is turned on. The
‘8.DEFAULTS’ menu allows for these configurations to be made, as well as the activation of the
remote echo canceller for voice calls.
4.3.1. Voice calls.
Typical phone circuits have a limited bandwidth between 300 and 4000 Hz. Unfortunately, most
of the voice’s energy is located in frequencies lower than 300 Hz, which are lost during
transmission through the phone line. This is why the audio signal has the typical telephone
sound, with substantial loss of low frequencies, perhaps, its most representative aspect.
AEQ S.A. offers equipment capable of transmitting signals between 50 and 3750 Hz. This
mode of operation is called “extended mode.” Evidently, this mode allows the band of
frequencies included between 50 and 300 Hz to be transmitted through the phone line. To
achieve this, the signal sent undergoes a 250 Hz frequency shift, improving the quality of the
signal received in its lower frequencies at the expense of the higher band. The bandwidth
transmitted is, thus, between 50 and 3750 Hz. The 250 Hz lost from the higher frequencies are
not very significant, given the logarithmic nature of the audio frequency response.
The translation of frequencies takes place by encoding the audio signal before it is sent to the
phone line. Decoding, i.e., the reverse frequency shift, takes place at the receiving end; the
decoding must be done by equipment design to accomplish this function. The decoded signal
has the original bandwidth (50-3750 Hz) without having suffered any alteration. Thus, greater
depth and clarity is achieved in the voice signal, even in those communications that take place
under the worst conditions.
• G711 Extended: Used to establish communications (in both directions) on non-digital lines
(basic telephone network). Equipment such as the AEQ TLE02, TLE02D, TH-02 MkII,
SWING or MPAC02 must be placed at the other end of the line, with the extended
frequency function activated.
• G711 Normal: In all other cases.
Access to the menu is through the SETUP section (front panel, no. 9)
- On the main screen, press NO (red) to access the SETUP menu.
- With the cursor arrows, go to the DEFAULTS option and press OK.
- With the cursor arrows, select G.711 and press OK
- With the cursor arrows, select the channel to be configured, and press OK.
- With the cursor arrows, select MODE option and press OK.
- With the cursor arrows, select NORMAL or EXTENDED mode.
DEFAULTS
G. 711
MPEG LII 128K
LINE 2
LINE 1
MODE
ECHO CANCELLER
J52
IMUX
EXTENDED
NORMAL
OFF
ON
OFF
ON
ECHO CANCELLER
MODE
EXTENDED
NORMAL