The CM-BH4W is a battery-powered, portable 4-wire communications unit designed for a multitude of TV and radio broadcast applications. Transformer Balanced I/O The CM-BH4W uses audio transformers on both its input and output, providing galvanic isolation against external interference, ensuring strong, clear communications every time. 4-Wire & IFB Modes In 4-wire mode, the unit operates as a 2-way intercom, with input audio routed to the headphone earpiece, and microphone audio directed to the output when the talk button is pressed. The output level is maintained at a peak level of +2dBu by built-in AGC. In IFB mode, input audio is routed to the output and is interrupted by the microphone signal when the talk switch is pressed. The talk switch can be easily converted from momentary to latching operation to suit your application. Low Battery Warning A low battery warning LED flashes when the 9V PP3 battery is depleted to 6V, giving ample time to change the battery. Additionally, the CM-BH4W automatically switches off when the headphone jack is removed, and the low-current circuit allows up to 150 hours of use from a single 9V PP3 alkaline battery. Technical Specifications for CM-BH4W/X From Mic Input to Line Output Mic Input Impedance: 1k5Ω unbalanced for 200Ω dynamic microphone Limiter Input Threshold: -60dBu Line Output Level: +2dBu Line Output Impedance: 150Ω transformer balanced From Line Input to Headphone Output Line Input Impedance: >10kΩ transformer balanced Input Gain/Volume: Adjustable from off to +10dB Maximum Input Level: +24dBu Maximum Headphone Output Level: +7dBu (ref. 9V battery voltage, <1% THD, 100Ω load) Minimum Headphone Impedance: 100Ω Connections Line Input: 1 x 3-pin female XLR socket (balanced) Line Output: 1 x 3-pin male XLR plug (balanced) Headphone (CM-BH4W): 1 x 6.35mm (¼") mono jack socket (unbalanced) Headphone (CM-BH4WX): 1 x 4-pin male XLR plug (balanced) Equipment Type CM-BH4W: 4-wire belt-pack headphone amplifier CM-BH4WX: 4-wire belt-pack headphone amplifier with 4-pin XLR headphone connector Physical Specifications 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 (packed): 23cm (W) x 13cm (D) x 8cm (H) 9.1" (W) x 5.1" (D) x 3.1" (H) Weight: Net: 0.3kg Gross: 0.4kg Net: 0.6lbs Gross: 1.0lbs