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This unit is used to synthesise a suitable mix to send to a telephone hybrid or codec to provide cue to a remote contributor.


A stereo output is taken from a mixer, together with a post-fade output from the mono telephone fader on the mixer. The caller audio is removed from the mixer output so that it can be sent to the telephone line via the hybrid.

The front panel is blank, apart from a power indicator. The rear has two electronically balanced XLR input connectors for the mixer output; these can be wired unbalanced. A third, similar in put is provided for the input from the telephone channel. There is an XLR output connector, also electronically balanced, which may be wired unbalanced without level loss. It has an associated pre-set level control. There is a multi-turn control to adjust the null level, the amount of the telephone channel which is subtracted from the mixer output signal, and a further multi-turn pre-set to adjust LF null. A switch enables a band-pass filter. Power is applied to an IEC inlet, with adjacent fuse and voltage selector switch.

Input: 0dB nominal, +28dBu maximum, 20kohms. Common mode rejection: greater than 60dB. Gain: -15dB to +12dB. Mix-minus null: Better than 40dB at 1kHz. LF null adjustment: Better than 40dB at 1kHz. Band-pass filter: 200Hz to 4kHz, 12dB/octave. Response: 20Hz to 22kHz +/-0.1dB. Distortion: 0.01% THD, 1kHz, +8dBu output. Noise: -90dB, 0dB gain, +6dBu output. Output: +28dBu maximum, 50 ohms. Power source: 110-120V or 220-240V AC 6W maximum. Dimensions: 280(w) x 108 (d) x 42 (h) mm. Weight: 1.1kg.

Included accessories: Handbook, AC power cordset with plug.
Optional accessories: The RB-RK1 is a 1U panel to rack-mount the device with the connectors inside the rack. The RB-RK2 (1U) rear-panel kit allows the device to be rack-mounted in reverse, with connectors outward.

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SONIFEX RB-MM1 MIX-MINUS GENERATOR, analogue, balanced   Stock code: 95-623
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SONIFEX RB-RK1 RACKMOUNT KIT Front panel, for 280mm wide types   Stock code: 95-659
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SONIFEX RB-RK2 RACKMOUNT KIT Rear panel - reverse mount, for 280mm wide types   Stock code: 95-638
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