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CM-CU21CP Commentator Accessories



CM-BH4WX Talkback, IFB & Commentary

Quick Overview

Belt-Pack 4-Wire Headphone Amp With 4 Pin XLR Headset Socket
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CM-BH4W Belt-Pack 4-Wire Headphone Amp

The CM-BH4W is a portable, battery powered 4 wire communication unit for use in a multitude of TV and radio broadcasting applications.

Transformer Balanced I/O

The CM-BH4W uses audio transformers at its input and output, providing galvanic isolation from outside interference, ensuring your communications are loud and clear, every time.

4-Wire And IFB Modes

In 4-wire mode, the unit acts as a 2-way intercom, with input audio routed to the headset earpiece, and microphone audio is routed to the output upon pressing the talk button. The output level is maintained at +2dBu peak level by a built-in AGC. In IFB mode, the input audio is routed to the output, and is interrupted by the microphone signal when the talk switch is pressed. The talk switch can easily be converted from momentary to latching operation to suit your application.

Low Battery Warning

A low battery warning LED flashes when the 9V PP3 battery has depleted to 6V, giving plenty of notice to swap the battery. In addition, the CM-BH4W automatically switches off when the headset jack is removed, and the low power circuitry gives up to 150 hours use from a single alkaline 9V PP3 battery.

CM-BH4WX Belt-Pack 4-Wire Headphone Amp With 4 Pin XLR Headset Socket

CM-BH4WX Top View

The CM-BH4WX is a version of the CM-BH4W with a 4 pin XLR headset connection instead of a stereo jack connector. In all other respects it is the same as the CM-BH4W.

Technical Specification For CM-BH4W/X

Mic In to Line Out

Mic Input Impedance:

1k5Ω Unbalanced for 200Ω dynamic microphone

Limiter Input Threshold:


Line Output Level:


Line Output Impedance:

150Ω Transformer balanced

Line In to Headphone Out

Line Input Impedance:

>10kΩ Transformer balanced

Input Gain/Volume:

Adjustable off to +10dB

Maximum Input Level:


Maximum HP Output Level:

+7dBu (ref 9V battery voltage, <1% THD, 100Ω load)

Minimum HP Impedance:



Line Input:

1 x XLR 3 pin female socket (balanced)

Line Output:

1 x XLR 3 pin male plug (balanced)

Headset (CM-BH4W):

1 x ¼” (6.35mm) mono unbalanced jack socket

Headset (CM-BH4WX):

1 x XLR 4 pin male plug (balanced)

Equipment Type


Belt-pack 4-wire headphone amplifier


Belt-pack 4-wire headphone amplifier with 4 pin XLR headset connector

Physical Specification

Dimensions (Raw):

12.5cm (W) x 6.7cm (D) x 4.8cm (H)

4.9” (W) x 2.6” (D) x 1.9” (H)

Dimensions (Boxed):

23cm (W) x 13cm (D) x 8cm (H)

9.1” (W) x 5.1” (D) x 3.1” (H)


Nett: 0.3kg  Gross: 0.4kg

Nett: 0.6lbs Gross: 1.0lbs