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Sonifex CM-TB8

Talkback Control Unit

The Sonifex CM-TB8 is a powerful and highly flexible self contained communications unit allowing multiple 4-wires and IFBs within a single 1U rack space.

Original price was: €3,670.Current price is: €3,480.

SKU: 106486
Original price was: €3,670.Current price is: €3,480.
Original price was: €885.Current price is: €845.
Original price was: €4,855.Current price is: €4,620.
Original price was: €4,545.Current price is: €4,320.
Original price was: €1,195.Current price is: €1,130.


Sonifex CM-TB8

8-channel talkback controller CM-TB8

The CM-TB8 is a powerful and highly flexible, self-contained communication unit for connecting multiple four-wire lines and IFB’s in a single 19″ rack unit. The device allows easy connection to any industry-standard talkback system, including the Line Listen unit Sonifex CM-TLL and the commentary systems CM-CU1 and CM-CU21.

The 8-channel talkback control unit CM-TB8 is ideal for use in OB vans and smaller studios and offers 8-channel four-wire communication within a 19″ unit on 1 U.

The unit has separate connectors for headsets on 5-pin XLRs as well as separate microphones/headphones on XLR and stereo headphone jack (TRS), with the currently selected connector indicated on the front panel. The input sensitivity can be set separately for each type of connection between +6dB and +68 for a wide variety of microphone types; 48V phantom power is also available. Minor adjustments to speaker volume can be made quickly with the rotary control on the front within a range of ±12 dB. This controller can be deactivated if required to protect against unintentional changes. A limiter automatically lowers the microphone gain if the level exceeds a preset value. The current talker level is displayed on the front panel, when it exceeds 0dB and +8dB. A separate rear output provides a balanced, level-corrected and level-limited microphone signal on a 3-pin XLR socket.

Each channel can be set separately for four-wire or IFB (Interruptible Foldback) operation. In four-wire mode, the input signal is routed to the monitor path (headphones/headset & speakers) with the level set on the monitor control. When the TALK button is pressed, the microphone signal is routed to the rear panel talkback output socket and the level of the loudspeaker path is attenuated to the value preselected with the dim control.

In IFB mode, the channel’s own four-wire input or one of the two external IFB inputs is routed to the talkback output jack and can be selected as the IFB signal. It is also possible to configure each channel so that the input signal is mixed with the microphone signal instead of being interrupted by it.

When a channel’s TALK button is active, the level of the signal sent to the speaker is automatically reduced by a pre-selectable amount, which can range from full level to complete cut-off. The TALK button is also used to signal calls. When the signal level on the 4-wire input of an inactive channel exceeds -12dB, the TALK button lights green. The TALK and GROUP TALK buttons are momentary on long press and latch on short press.

The Group Talk function enables several preselected channels to be activated at the same time. All preset channel buttons will light, as will the GROUP TALK button. Any channel can be included or excluded from the Group Talk feature; in the factory setting, all channels are included.

Each channel has its own monitor volume control, which determines the level at which the signal is mixed with that of the other active channels. The mixed signal is routed to the speaker and headphone channels; the Monitor control determines its overall level. For the speaker path, front panel controls for mute and dim level are available. A connection for an external speaker on the rear provides a level-controlled output signal. When this output is used, the internal speaker is muted.

The device has a built-in test tone generator for line testing and channel identification. The generator works in two modes: In manual mode, the signal is routed to a channel when the corresponding TALK button is pressed. In Auto mode, an individual pulse is generated for each channel to identify it.

A remote rear output provides a ‘tally’ indication for active talk channels and group talk status via open collector outputs. Further ‘tally’ outputs show the status of the dim and mute functions for the loudspeaker, as well as the activity of the call indicators, which are driven by the input signal.

A separate remote input offers an additional option for call display of the input signals in each channel. When an input is activated, the corresponding Talk button flashes. Inputs for remote control of the dim and mute functions for the loudspeaker are also available.

As an option, a telephone add-on card (CM-TB8T or CM-TB8G) can be installed, which allows the connection of up to two channels to a landline or GSM. This allows the user and talkback users to communicate with a connected caller, with both four-wire and IFB operation possible.

The CM-TB8 offers a variety of user configurable options. 6 configuration presets can be saved and recalled later. Two of these configurations cannot be overwritten. The other four preset slots are for storing custom settings. This enables the device to be preconfigured for different application scenarios that can be called up immediately. The device’s Ethernet port allows configuration parameters to be edited via the built-in web server, and a local configuration mode allows many options to be set without a PC.

The CM-TB8 talkback control unit is powered by a universal mains connection with 85-264V AC at 47-63Hz.

Features of the CM-TB8 8-Channel Talkback Controller

  • 8-channel talkback control unit in a 19″ housing with 1U
  • Separate microphone and headset inputs with phantom power and individual gain settings
  • Microphone talk level can be adjusted on-the-fly or preset
  • LEDs for talk level and built-in limiter
  • Configurable ‘Group Talk’ function
  • IFB (interruptible foldback) and direct four-wire operation selectable in each channel, optionally with mix function for the talkback microphone
  • 2 external IFB (Interruptible Foldback) inputs available per channel
  • Optional telephone hybrid or GSM port for direct communication via a telephone connection
  • Individual monitor level control for each channel
  • Microphone output path with level adjustment and signal limitation
  • Ethernet connection for remote configuration via built-in web server
  • 6 memory locations for configurations, 4 of which are user sets
  • Front speaker and separate path for external speaker
  • Mute and dim function for speakers, also remote controllable
  • Remote ‘tally’ outputs to indicate individual channel activity
  • Remote inputs for call indication on each channel
  • Built-in test tone generator for channel identification

Specifications CM-TB8

microphone input

Reinforcement range: +6dB to +68dB
Maximum input level: -6dBu
Common mode rejection: >60dB
Frequency Response: ±0.5dB 20Hz to 15kHz reference 50dB gain @ 1kHz

headphone output

Reinforcement range: -60dB to +18dB
Maximum output level: +18dBu
Frequency Response: ±0.5dB 20Hz to 15kHz

Four-wire and IFB inputs

Maximum input level: +18dBu
Frequency Response: ±1dB 20Hz to 15kHz

Talkback outputs

Maximum output level: +18dBu
Frequency Response: ±1dB 20Hz to 15kHz


Output power: 6W
Rush: more than 80dB below maximum output level
Volume: Mute to full level via front panel controls


Microphone: XLR 3-pin female (electronically balanced)
Headphones: 6.35 mm stereo jack
Headset: XLR 5-pin female (electronically balanced)
Four-wire inputs: 8 x XLR 3-pin female (transformer balanced)
IFB inputs: 2 x XLR 3-pin female (transformer balanced)
Talkback outputs: 8 x XLR 3-pin male (transformer balanced)
Microphone output: XLR 3-pin male (electronically balanced)
Speaker output: 6.35 mm stereo jack
Remote inputs: 15 pin ‘D’ Sub socket
Remote outputs: 15 pin ‘D’ Sub socket
Ethernet: RJ-45, 10/100Mbps
Phone: 4 x RJ11 6/4 (2 x line, 2 x handset), only available on the CM-TB8T
Power connection: Universal, filtered IEC connector, continuous operation 85-264VAC, 47-63Hz, 25W
Fuse: Anti surge fuse 2A 20×5 mm

device type

CM-TB8: 8-channel talkback controller
CM-TB8T: Additional card with 2 x telephone hybrid
CM-TB8G: Additional card with 2 x GSM

mass and weight

including connectors:
48 cm (W) x 34.0 cm (D) x 4.2 cm (H) (1U)
19” (W) x 13.4” (D) x 1.7” (H) (1U)
Packed up: 57 cm (W) x 52 cm (D) x15cm (H)
22.4” (W) x 20.5” (D) x 5.9” (H)
Weight: Net: 5.54 kg Packed: 6.5 kg
Net: 12.2lbs Packed: 14.3lbs


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