Used Clear-Com TW-12B Communications

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Clear-Com TW12B Intercom System Interface - 2 Available


Clear-Com’s TW-12B intercom system interface is designed for connecting one intercom system to another, without compromising the audio quality of either system. The TW-12B solves all problems that can arise when connecting, for example:

  • a mobile production unit’s intercom system to an intercom in a nearby building
  • same-type systems located in two different buildings
  • to any “unknown” interface, such as a TV camera
  • concert hall’s intercom to touring group’s intercom

Transparent Isolation Between Systems

The unique TW-12B completely eliminates hums and buzzes caused byground loops (which occur when you interface two systems that use different power supplies or grounds). The TW-12B compensates not only for level differences between systems, but for varying impedances caused by transformers and capacitance on the lines.

The completely transparent TW-12B provides an electrically isolated interface between the two intercom systems. Either “side” of the interface can connect to a Clear-Com intercom system or an RTS intercom system, allowing Clear-Com-to-Clear-Com, Clear-Com-to-RTS, and RTS-to-RTS combinations. In addition,the TW-12B passes through and translates “call” signals, Clear-Com-to-RTS andvice versa.

The interface consists of two identical, 2-wire-to-4-wire hybrid networks which break the ground loops that occur when two systems are run from separate power sources. The audio paths are transformer-coupled, and the signaling circuits areopto-isolated.

Fast, Easy, and Accurate Setup

The operator can quickly set up the TW-12B by using a standard intercom headset and the TW-12B’s built-in setup tone. The TW-12B is capable of a range of null adjustments, allowing it to adapt to a wide variety of line conditions, line lengths, and impedances.

Clear-Com’s innovative, nulling system provides up to 40 dB null. The TW-12Bprovides each side of the system with null adjustment controls that allow adjustment even when the system is operating.

The rear panel of the TW-12B contains a pair of 3-pin XLR connectors (one male, one female) for each side of the interface.

Call Signal Translation

The TW-12B interface receives "Call" signaling in the appropriate form (DC level for Clear-Com, tone for RTS,) decodes it, and passes it to the other side of the interface, via an optical coupler. The receiving side of the interface sends the signal appropriate for the connected intercom.


A recessed Send Gain control allows an adjustment of +/- 6 dB for each side of the interface if necessary.


Each side of the TW-12B is powered directly by the intercom system to which it is connected. The unit draws about the same amount of power as a belt-pack. If either system is disconnected, the power loss immediately shuts down the associated electronics, eliminating any unwanted noises on the operating intercom side. The TW-12B front panel provides an LED power indicator for each side of the interface.


  • Eliminates grounding problems between intercom systems
  • Matches gain between systems
  • Provides system isolation for: Clear-Com to Clear-Com; Clear-Com to RTS; RTS to RTS
  • Passes through and translates signaling
  • Provides superior hybrid nulling– up to 40 dB
  • Setup tone allows adjustment during operation
  • Powered from connected systems
  • Uses just one rack space


    • Line Characteristics, Clear-Com
      • Level: -13dBv nominal, 0 dBv max.
        • before clipping*
      • Clipping Level: +3 dBv min.
      • Impedance: >10 kΩ bridging
    • Line Characteristics, RTS
      • Level: 0 dBv nominal
      • Clipping Level: +5 dBv min.
      • Impedance: >10 kΩ bridging
    • Signaling, Clear-Com
      • Receive: 4 VDC min. on audio line
      • Send: 11 VDC min. on audio line
    • Signaling, RTS
      • Send Frequency: 20 kHz. +/-100 Hz
      • Receive Frequency: 20 kHz. +/-500 Hz
    • General Characteristics
      • Frequency Response: 200 kHz - 10 kHz, +/-3dB
      • Nulling Capability (2-wire && 4-wire),
        • Line Length: 0 to 4,000 feet
        • Line Impedance: 120 - 600 Ω
        • Low Frequency: L&C of the 2-wire line
        • Depth of Null: >30dB, 200 Hz - 8 kHz
      • Isolation,
        • Side to Side: >10 MΩ
        • Either Side to Chasis: >10 MΩ
      • Power Consumption:
        • ≈ 50 mA at 20 - 30 VDC
      • Connectors,
        • Front panel: headset, (1) 4-pin, D4M
        • Rear panel: (4) 3-pin XLRs (2 male, 2 female)
          • Each side has one each male and female for loop-through
        • Dimensions:
          • 1.75" H x 19" W x 6" D (44 x 483 x 152 mm)
        • Weight: 4.0 lbs (1.8 kg)

Specifications subject to channge without notice.

*0dBv is referenced to 0.775 volts RMS.