Dual Listen Functionality

The base stations's main audio board has the option of placing additional parts to enable dual listen. Dual listen allows the mixing of the intercom channels. The mixing will occur lo- cally, within the base station, and is only heard on that base station's beltpacks. The user will have the ability to enable/dis- able the mix of I/C A into I/C B or vise versa. If you have TR-825 beltpacks, there is no need to install this base option. The level of the mix can be controlled at the TR-825 via the two volume controls.

They will also have the ability to control the level of the mix (-4 dB to -24 dB down from main channel). Removing two surface mount resistors and installing two SPDT switches and two potentiometer enables dual listen. The parts to be installed are shown in Table 1. The two resistors on the board to be re- moved are in Table 2.

Board

 

 

 

 

 

 

 

 

 

 

Designator

 

Description and Function

Value

 

 

Manufacturers, Part No.

 

 

 

 

 

 

 

 

 

VR5, VR6

 

Potentiometers

 

20kW - 25kW

 

Bourns, 3309P-1-203

 

 

 

VR5 = Controls I/C A into I/C B Mix

 

 

CTS, U262R253B

 

 

 

VR6 = Controls I/C B into I/C A Mix

 

 

Piher, PT10LV10-203A2020

 

 

 

 

 

 

 

 

 

S6, S7

 

Switches

 

SPDT

 

E-Switch, 500ASSP1M2RE

 

 

 

S6 = Enable/Disable I/C A into I/C B Mix

 

 

E-Switch, EG1218

 

 

 

S7 = Enable/Disable I/C B into I/C A Mix

 

 

Alcoswitch, TSS11DGPC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1

 

 

 

 

 

 

 

 

Parts to be Installed by User to Enable Dual Listen

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Board

 

 

 

 

 

 

 

 

 

 

Designator

 

Description and Function

 

Value

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R295

 

Resistor, Default if mix components not installed

 

10k

 

 

 

 

R296

 

Resistor, Default if mix components not installed

 

10k

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2

Parts to be Removed by User to Enable Dual Listen

The listed manufactures and part numbers in Table 1 are those that the audio board was laid out for and thus the hole pattern used. Several of these parts may be found at Digi-Key and other distributors. Trim the leads on the parts so they can not hit the metal case. Locations to place these components are provided on audio board part number 750608.

The audio board part number is located on the lower left hand side of the board if facing the front of the unit. The locations where the components can be installed are on the upper right hand side of the board. See Figure 22 for the locations. Board part number 750541 does not have locations to place compo- nents, however, modification documents may be obtained from Telex Communications for those who wish to modify older audio boards for dual listen.

BACK

 

 

 

 

B INTO A

 

 

 

MIX

 

 

 

 

 

MIX

 

 

LEVEL

 

 

 

 

VR6

 

ON

 

 

 

 

OFF

 

 

 

 

 

 

B INTO A

 

 

 

S7

 

MIX

 

R298

R296

IF PARTS INSTALLED

 

ON

 

 

OFF

 

REMOVE R296

 

 

 

 

ON

 

MIX

 

S6

 

OFF

LEVEL

 

 

 

A INTO B

 

ON

 

MIX

 

 

 

 

 

 

VR5

 

 

 

 

 

OFF

 

 

 

 

 

 

 

 

R297

R295

A INTO B

 

 

 

MIX

 

 

 

 

 

IF PARTS INSTALLED

 

 

 

 

 

REMOVE R295

750608

REV X

750608

REV X

879416- 1 REV J

879416- 1 REV J

 

 

FRONT

 

 

 

 

 

Figure 22

Audio Board Part Number and Dual Listen Component Locations

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Image 27
Telex TR-825, BTR-800 dimensions Dual Listen Functionality, Parts to be Removed by User to Enable Dual Listen