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Automatic Changeover

The 5700ACO Automatic Changeovers are intended for use with two 5700MSC Master Clock/Sync Generators. The 5700ACO system uses mechanically latching relays to ensure maximum reliability and minimal disruption in the event of any failure, even power failures. The complete system provides the highest level of security for television station video and time synchronization systems. The 5700ACO is a 2RU ACO for all outputs of the 5700MSC. Two power supplies are included as a standard feature, to alleviate any single point of failure concerns.

There are three switches behind the front panel for added security. There is an AUTO/MANUAL switch, a GPI/FRONT PANEL switch and an A/B select switch for manual changeover. In automatic mode, all signals from both 5700MSC are monitored to detect any abnormal signals. For example, if a level, pulse width, phase, time code error or other abnormality is detected, the 5700ACO's circuitry will trigger and the entire bank of signals will be switched to the backup 5700MSC. In manual mode the changeover can be operated from a GPI or from the front panel switch. LEDs provide status information as to the health of the two 5700MSC, together with indication as to which one is active. In addition, two GPO outputs indicate which master is active and when the inputs from both masters are not the same.

The 5700ACO features selectable voting via VistaLINK® for autochangeover features. Individual inputs may selectively be included or excluded in the voting process to drive autochangeover logic.

Each 5700MSC is equipped with two GPI inputs and two GPO outputs. To facilitate installation, these connections are brought through to a 2x6 pin terminal block on the 5700ACO. The outputs from the 5700MSC are passed straight through the 5700ACOs. The inputs to the 5700MSC's are internally split by a 'Y' connector, to ensure that both 5700MSC's receive the same GPI contact closures.


  • Three protected switches select automatic, front panel or GPI activation of changeover
  • Front panel status LEDs show the health of each of the inputs
  • Front panel status LEDs show the operational modes of the changeover
  • Redundant power supply standard
  • Push button to show cause of last changeover
  • Dual hot-swappable power supplied and fans
  • Hot-swappable main board
  • GPIO input/outputs
  • Automatic changeover is a voting system based on which source has the most valid signals and that the valid signals on the present master are also on the backup
  • VistaLINK® control for device configuration and status monitoring
  • Six video/sync or other coaxial signals
  • 10MHz frequency reference
  • Word clock output
  • DARS and 3 AES
  • Two Longitudinal (LTC/EBU) timecode outputs
  • Four SD/HD/3G outputs


LTC/IRIG Inputs and Outputs

Standard SMPTE ST 12-1 frame rate set by 5700MSC or IRIG-B
Inputs 2 per 5700MSC
Outputs 2
Inputs Female DB15
Outputs 3-pin male XLR type
Signal Level Set in 5700MSC

Coaxial Inputs and Outputs

Type Depends on signal connected from 5700MSC
HD-SDI, SD-SDI, Analog TG, AES, DARS, bi-level or tri-level sync, colour black, 10MHz, Word Clock
Number 12 groups each consisting of two inputs and one output
Connector BNC per IEC 61169-8 Annex A

ACO General Purpose Inputs and Output

GPI1 Master select in Manual GPI control mode
Low: Selects Master A
High: Selects Master B
GPI2 Dual GPO mode.
GPI 1 Low, GPI 2 High selects Master A
GPI 1 High, GPI Low selects Master B
Otherwise no change
GPO1 Low: Master A is selected
High: Master B is selected
GPO2 Low: Master A and Master B differ or PSU failure
High: Master A and B have equivalent signals
Inputs Opto-isolated input with internal pull-up to +5V
Outputs Normally closed relay to ground
10kW internal pull-up to +5V when relay is in active position
Connector 4 pins plus 2 ground pins on 12-pin removable terminal block
Signal Level +5V nominal

MSC General Purpose Inputs and Output

Inputs 2 GPI inputs connected to both Master A and Master B through AUX I/O
Outputs 2 GPI outputs connected from Master A through AUXI/O A
2 GPI outputs connected from Master B through AUXI/O B
Connector 6 pins on 12-pin removable terminal block
Signal Level As specified in 5700MSC manual

1000BASE-T Control Network

Quantity 1
Network Type IEEE 802.3 (10BASE-T)
IEEE 802.3u (100BASE-TX)
IEEE 802.3ab (1000BASE-T)

Changeover conditions

Changeover is a voting system based on which source has the most good signals and that the good signals on the current master are also present on the backup master. The input signals are considered good according to the following criteria:
Video Level below 70 IRE
Sync H timing detect
10MHz 3dB level below 0.3V p-p
DARS Sync word error
LTC Level below 0.3V p-p
Incorrect sync word


Power Auto ranging 100 – 240V AC, 50/60Hz, 40 watts
Configuration Dual redundant supplies
Fuse Rating 250V, 1A, time delay
Safety TüV Listed
Complies with EU safety directives
EMI/RFI Complies with FCC Part 15 Class A
Complies with EU EMC Directive


Dimensions 19" W x 3.5" H x 11.5" D
(483mm W x 90mm H x 292mm D)
Weight 16lbs (3.5kg)

Ordering Information

5700ACO 2RU Automatic Changeover System complete with 2 power supplies, 2 power cords and 2 DB15 cables (BNC cables not included)