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3G/HD/SD/ASI & 4K Change-over with Clean Switch & ALC

The HCO-3901 is a 3x1 3G/HD/SD/ASI change-over which support 16 channels of embedded audio and metadata. The module can perform a video and audio “Clean and Silent Switch” between sources using the CS option (not available with ASI signals). In the event of a power failure, the PGM signal is protected by relays fitted on the rear module, maintaining the integrity of the selected signal at the output. Relays are fully controllable via GPI. With the addition of the HCO-3901-3DRP-R-EX rear panel, the HCO-3901 now supports paired outputs for 3G/HD/SD SDI (single outputs only for ASI). The latest addition, HCO-3901-4K, supports 4K UHD Quad-Link SDI change-over with support for embedded audio and...


  • Two primary inputs: IN 1 and IN 2 plus one secondary: IN 3
  • Four outputs: main program and three previews
  • Eight outputs (with EX rear): paired outputs for main program and each of the three previews (single outputs only for ASI)
  • Supports 3G, HD (1080i50/59.94, 720p50/59.94) and SD (525, 625) or ASI input and output
  • Supports 4K UHD Quad-Link SDI with optional HCO-3901-X4RP remote control panel
  • Electronic switching with relay backup (on rear module) maintains selected input with power loss for Primary inputs IN 1 and IN 2
  • Automatic mode using internal signal analysis with alarm parameters for IN 1 and IN 2
  • Manual change-over by local frame controller, iControl, iControl Solo or GPI (3DRP rear) for 3 inputs
  • Alarm reporting to iControl facility monitoring and control system
  • Compatible with iControl end-to-end A/V fingerprint analyzer for lip sync error detection and measurement (not available with ASI signals)
  • GPI in and out (IN 1, IN 2, IN 3, auto, bypass)
  • Optional clean switch function (video and 16 channels of audio) for IN 1 and IN 2 (not available with ASI signals)
  • Optional on-board automatic loudness control by Grass Valley (not available with ASI signals)
  • Reference input with passive loop through (3DRP rear only)
  • Two line timing window with CS option (not available with ASI signals)
  • Thumbnail and audio level meter streaming for IN 1, IN 2 and PGM OUT (not available with ASI signals)
  • Loudness compliant to EBU R128-2014, ATSC A/85:2013 (FCC CALM compliant) and ARIB TR-B32 (ITU-R BS.1770-3)


SDI (Inputs/Outputs)
SDI Standards:
  • SD: SMPTE ST 259-C (270 Mb/s) 
  • HD: SMPTE ST 292 (1.485, 1.485/1.001 Gb/s) 
  • 3G: SMPTE ST 425 (2.970, 2.970/1.001 Gb/s) 
  • DVB-ASI: EN 50083-9 
Supported Formats:
  • SD: SMPTE ST 125: 480i59.94, 576i50 
  • HD: SMPTE ST 274: 1080i59.94, 1080i50 
  • HD: SMPTE ST 296: 720p59.94, 720p50 
  • 3G: SMPTE 425 level A (mapping 1): 1080p59.94, 1080p50 
  • 4K UHD: Quad Link 3 Gb/s SMPTE ST 425-5 (3G-SDI Link 1, Link 2, Link 3 and Link 4): 1080p59.94, 1080p50 
Cable Length1
  • 350m (1,148 ft.) Belden 8281 at 270 Mb/s 
  • 130m (426 ft.) Belden 1694A at 1.485 Gb/s 
  • 90m (295 ft.) Belden 1694A at 2.970 Gb/s 
Return loss: 
  • >15 dB up to 270 MHz (PGM out)3
  • >15 dB up to 1.5 GHz (IN 3, PVW out)3
  • >12 dB up to 1.5 GHz (PGM out)3
  • >10 dB up to 1.5 GHz (IN 1, IN 2)2
  • >10 dB up to 3 GHz (IN3, PVW out)3
  • >8 dB up to 3 GHz (IN 1, IN 2)2
  • >7 dB up to 3 GHz (PGM out)3
  • SD/HD <0.2 UI (alignment jitter) 
  • 3G <0.3 UI (alignment jitter)


  • Signal:
    • SMPTE ST 170/SMPTE ST 318/ITU 624-4/BUT 470-6 or composite sync
    • SMPTE ST 274/SMPTE ST 296 tri-level sync
  • Return loss: >35 dB up to 5.75 MHz
GPI (10)
  • Connector: HD-15, opto-isolated, common ground
  • GPI IN (5): Contact closure to ground
  • GPI OUT (5): Contact closure to ground
  • External pull up Voltage: 3.3V to 24V max
  • External GPI power: 5V nominal
  • Signal path: 10 bits
  • Latency: 0.4 ns without CS option and ALC option
  • Maximum of 2 lines with CS or ALC option
  • Quantization: 20-24 bits
  • Sampling: 48 kHz, synchronous
  • Number of channels: 16, 4 groups
  • Audio latency:
    • 0.4 ns without CS option and without ALC option
    • Add 1 ms if CS option is enabled
    • Add 1 ms if ALC option is enabled
  • Power: 10W
    • Note 1: Cable length and return loss specifications will be reduced when using the output protected by the bypass relay, refer to the manual for more details.
    • Note 2: Input protected by relay.
  • Note 3: PGM output protected by relay.


Densité 3 Frame Description
HCO-3901 3G/HD/SD change-over with optional clean switch and ALC
HCO-3901-3SRP-R Single rear connector with bypass relay
HCO-3901-3DRP-R Double rear connector panel with bypass relay
HCO-3901-3DRP-R-EX Double rear connector panel with bypass relays and paired outputs
Densité 3 and Densité 3+ FR4 Frame Description
HCO-3901-4K 4K UHD change-over with optional clean switch and ALC HCO-3901-4K consists of: 4x HCO-3901, 4x HCO-3901-3DRP-R, 1x HCO-3901-X4RP
HCO-3901-X4RP Remote control connector panel for Quad Link 4K UHD
Options (software) Description  (Note that all of the following options are not functional with ASI signals)
HCO-3901-OPT-CS Clean switch option
HCO-3901-OPT-ALC-2 2-channel on-board ALC option
HCO-3901-OPT-ALC-6 6-channel on-board ALC option
HCO-3901-OPT-ALC-8 8-channel on-board ALC option
HCO-3901-OPT-ALC-16 16-channel on-board ALC option
Options (hardware) Description
NSH15M HD-15 to terminal block adapter
Options for HCO-3901-4K Only Description
HCO-3901-OPT-CS Clean switch option (4 licenses required for HCO-3901-4K)
ALC Any software option from above is allowed, but only one is required and applies to the first HCO-3901 (Q1) card in the HCO-3901-4K KIT



HCO-3901 & HCO-3901-4K: 3G/HD/SD/ASI and 4K UHD Change-Over with Clean Switch and ALC Datasheet

The HCO-3901 from Grass Valley, a Belden Brand, is a 3x1 3G/HD/SD/ASI change-over which support 16 channels of embedded audio and metadata.



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