Sonifex analogue talkback systems are used for general talkback between studios. The use DC signalling, also known as ground lifting or ground signalling, to communicate with each other. These units have been designed to be installed in locations throughout multiple studios and linked to one another, with each unit being able to talkback to up to 6 others.
CM-TB8 is a talkback control unit providing 8-channels of 4-wire communication, designed for OB trucks or small studios and housed in a single 1U rackmount unit. CM-TB8 is a powerful and flexible self-contained communications unit that is compatible with talkback systems including Sonifex CM-TLL line listen unit along with the CM-CU1 and CM-CU21 commentator units.
The unit has individual connections for both a headset on 5-pin XLR, and microphone/headphones on XLR/stereo TRS jack - the current selection is indicated on the front panel. The gain setting for each input type can be individually set between +6dB and +68dB allowing for a wide range of microphone types, including those that require +48V phantom power. Small talk level adjustments can be made using the front panel rotary control which has a maximum adjustment range of +/-12dB. This adjustment can be disabled if required to stop inadvertent changes. A level limiter automatically adjusts the microphone gain if the signal level exceeds a preset level, and the current talk level is indicated on the front panel when it exceeds 0dB and +8dB. A separate output on the rear panel provides a balanced, gain adjusted and level limited microphone signal on 3-pin XLR.
Each channel can be set to either 4-Wire or Interruptible Foldback operation. In 4-Wire mode the 4-Wire input signal is routed to the monitor channel (headphones/headset & loudspeaker) at the level set by the monitor level potentiometer. When the TALK button is pressed, the microphone signal is routed to the rear panel talkback output connector, and the level of the feed to the loudspeaker is reduced to the level preset by the dim potentiometer. The group talk function allows a group of preselected channels to be activated simultaneously. The buttons on all activated channels are illuminated as is the GROUP TALK button. Each channel can be included or excluded from group talk function, and by default, all channels are included.
Each channel has a separate monitor level control which sets the level of the signal that is mixed with the other active channels. This signal is then fed to both the loudspeaker and headphone monitor channels and its overall level is controlled by the monitor level potentiometer. The 6W loudspeaker has front panel mute and dim attenuation level controls. An external loudspeaker connection on the rear panel provides a level adjusted output and when this output is used, the signal to the internal speaker is muted.
The unit also features a built in line-up tone generator for easy channel identification and cabling checks. A rear panel mounted remote output connector provides a ‘tally’ indication of active talk channels and group talk status via open collector driven outputs. Other ‘tally’ outputs indicate the status of the loudspeaker dim and mute controls and also if any of the audio input activated call indications are active.
Microphone gain range: +6dB to +68dB. Maximum input level: -6dBu. C.M.R.R: Greater than 60dB. Headphone gain range: -60dB to +18dB. Maximum output level: +18dBu. Frequency response: 20Hz to 15kHz, +/-0.5dB. 4-Wire/IFB maximum input level: +18dBu. Frequency response: 20Hz to 15kHz, +/-1dB. Talkback maximum output level: +18dBu. Frequency response: 20Hz to 15kHz, +/-1dB. Loudspeaker output: 6W. Noise: More than 80dB below full output. Dimensions (WxDxH): 480 x 340 x 42mm. Weight: 5.54kg.
Optional accessories: CM-GM2 gooseneck microphone.
Discontinued
Housed in a 2U rack-mounting case, TB-6R has been designed to allow communication with up to six other locations - seven locations in total. On the front panel there are six buttons for talkback selection and two for external inputs. A volume control adjusts the levels of both speaker and headphones. While a button is pressed, the button is illuminated and the talkback signal is active to that location. The buttons work with both a momentary and latched operation. If held down, the selection is cancelled when released, otherwise the button is alternate action. When talkback is incoming, the external inputs can be either muted or mixed with the incoming signal, depending on the setting of an internal jumper.
The signal sent to the other locations can be from the onboard electret microphone on the front panel or a separate external microphone signal. Incoming signals can be monitored using the front panel mounted loudspeaker, or headphones. When the headphones are used, the speaker is automatically muted, or, the monitor speaker can be muted via a remote contact. Two external sources may be monitored for example, for confidence monitoring, or for listening to a station feed. The front facing panel also has the loudspeaker grille and an XLR for the external microphone connection.
On the rear is an associated preset gain control, a switch to select microphone source, the 6.35mm stereo headphone socket, two stereo, balanced external inputs via a 9-pin D-sub connector which also carries remote control signals, two RCA (phono) sockets for external input 2, and a preset level control for the incoming talkback signal. In addition there is an IEC power inlet, fuse and the 15-pin D-sub connector to connect talkback input and outputs to the other locations.
Internal jumpers can be configured to use alternative sources rather than the onboard microphone amplifier and to feed the monitor signal to other systems such as a mixer, rather than the internal monitor amplifier. The intercom is then used for switching and monitoring external inputs.
Sonifex TB-6R intercoms use ‘phantom’ or ‘common-mode’ DC signalling, where a ground is placed on the centre-tap of a transformer, to communicate, so are compatible with many of the other talkback systems in use. A sending station places an earth on the centre-tap; this is detected by the receiving unit, which then un-mutes (and provides a DC signal to dim local monitors if required). Each station has a single listen line input and six outputs. When any of the talk buttons is pressed, outgoing talkback and signalling is sent to the selected line. The ‘send’ circuits to a single receiving unit are simply connected in parallel to the input of the receiving unit. Since sending impedance is quite high, and receiving input is quite low, the effect is to mix any incoming talkback signals.
Input impedance: External inputs; greater than 30kohms unbalanced, 40kohms balanced. Input impedance: Microphone; 1.5kohms. Input gain: Microphone; 74dB to 53dB. Input gain: Talkback; 9dB to -28dB. Headphone output: 150mW into 32-600ohms. Gain: Headphone output; 9dB to bellow-60dB (off). Power source: 85V - 264V AC, 47-63Hz. Dimensions (HxWxD): 89(2U) x 483 x 185mm. Weight: 2.6kg.
Included accessories: Manual and IEC power cordset.
Optional accessories: Gooseneck microphone. See Canford dynamic gooseneck microphones.