RTS TR-240 Especificaciones descargar pdf (Pagina 31)

Echo Cancellation

When any digital intercom system is connected to a 2-wire

system, there will be some “echo”, called network (line) echo,

due to the audio latency of that digital intercom system. In a

2-wire intercom system, the transmitting and receiving audio

signals exist together on a single wire. At the base station, a

“nulling” circuit is used to isolate the transmitting and receiving

signals. Network (line) echo occurs because the nulling circuit

alone is insufficient at separating the transmit and receive signals

and a small portion of the 2-wire transmit signal is also present on

the 2-wire receive signal which gets transmitted back to the

beltpack devices. For digital systems, echo cancellation is used to

further isolate the 2-wire transmit and recieve signals.

The BTR-240 base station features automatic and adaptable

echo cancellation (AAEC). The BTR-240 will quickly “learn”

and adapt to the echo characteristics of a connected 2-wire

system. Once the echo has been characterized, the BTR-240 will

assist in removing echo for improved communication.

The learning process takes approximately three to five seconds.

During this time, users should talk only into the BTR-240 local

headset, or associated TR-240 beltpacks, and the users on the

2-wire beltpacks should have their talk features disabled. This

procedure only needs to be performed initially when the 2-wire

first becomes activated.

After the echo cancellation has learned the characteristics of the

system, it will continuously adapt as changes to the system occur.

NOTE: Excessive noise or talking on the 2-wire side will

prevent the echo cancellation from learning and echo

will be present. As soon as the audio on the 2-wire side

becomes quiet enough, the echo cancellation

learning cycle will complete and the echo will be

removed.

Other Sources of Echo

Users need to be aware that there are several sources of echo. In

addition to line echo, there is also a type referred to as acoustic

echo.

Acoustic echo is commonly heard by a user when their audio

arrives at a second user’s headset and a portion of that audio in the

headset gets back into the second user’s microphone (by having

the volume and/or microphone gain set fairly high or by using a

headset with poor acoustical isolation). That portion of audio is

then transmitted back to the first user and heard as “echo”.

To reduce the effects of acoustical echo, users should first turn off

their <TALK> buttons one by one to identify which devices are

the sources of echo. Once the source(s) have been identified,

acoustical echo is avoided by decreasing the headset volume,

microphone gain, sidetone level, or increasing the squelch

settings of that device.

NOTE: Do not leave any headsets unattended with the

<TALK> button enabled. When headsets are removed,

always ensure that the microphone path is disabled.

4-Wire (Matrix) Intercom

The BTR-240 base station has the ability to interface to two,

4-wire external audio intercom systems. As shown in Figure

5-21, these RJ-11 jacks are designated as “Intercom 1” and

“Intercom 2” on the rear panel.

The 4-wire intercom may be used at the same time as the 2-wire

intercom.

The 4-wire intercom uses two pairs of wires to support one

full-duplex audio channel. One pair for the sending balanced

audio and one pair for the receiving balanced audio. Refer to

Section 11 for the 4-wire hardware specifications and pinouts.

Many Matrix systems also have an additional pair of wires to

transfer data between devices. The BTR-240 4-wire connection

does not use these data lines and supports only the audio

interface.

Steps to change the 4-Wire Intercom Settings:

1. From the Status Screen, press <MENU> on the BTR-240

front panel.

2. Using the <UP>/<DOWN> buttons, navigate the cursor to

the “Intercom Settings” menu option, then press <SET> to

select the menu.

3. Once again, using the <UP>/<DOWN> buttons, navigate

the cursor to the “4W Intercom” menu option, then press

<SET> to select the menu.

5-7

Figure 5-23

Intercom Menu Screen

2W Intercom 2W Intercom

-> 4W Intercom -> 4W Intercom

Figure 5-22

Main Menu Screen 2

Speaker SettingsSpeaker Settings

-> Intercom Settings-> Intercom Settings

Auxiliary Settings Auxiliary Settings

Prev.... Prev....

PUSH

INPUT

BTR-240

Bosch Security Systems, Inc.

S.N. 00000

MADE IN USA

PROGRAM

10 26

SPEAKER

PUSH

2 WIRE

AUDIO

4 WIRE

INTERCOM 1

PUSH

2 WIRE

AUDIO

4 WIRE

INTERCOM 2

AUXILARY

OUTPUT

12/15/VDC

1.5A

IP: 192.168.1.1

BTR-240

Bosch Security Systems, Inc.

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AUDIO

4-Wire (Matrix) Intercom

Figure 5-21

4-Wire Intercom

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RTS TR-240 Especificaciones Pagina 31

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