Crystal Vision's clean switch uses two framestore synchronizers and loss of reference protection to keep broadcasters on air

Crystal Vision’sSafe Switch 3G provides clean and intelligent 2 x 2 switching between two 3Gb/s, HD or SD sources containing up to four groups of embedded audio and is the only way to guarantee a clean switch. The full framestore synchronizer on each input allows it to correct for any timing difference between the two inputs resulting in no disruption to the output picture when a switch takes place, while it can even lose the reference and not affect the output. It can be used for planned maintenance switches to manually re-route a good signal around broken equipment, or as an intelligent emergency transmission switch with the option of selecting from 16 different fault conditions to automatically trigger the switch. Available in two versions – as Safe Switch 3G and Safe Switch-L 3G – it provides a robust, one-board solution that replaces a switch and two synchronizers, simplifying system designs and saving broadcast engineers both money and rack space.

Safe Switch 3G can be switched either automatically or manually. To help broadcasters ensure continuity of service, Safe Switch 3G is ideal for use on the final output stage of a transmission system, before the signal gets to the MPEG encoder. Typically the backup signal going into the switch will have gone a simplified route compared to the main programme, resulting in a time difference between the two feeds which can upset the MPEG encoder on a switch to backup. Safe Switch 3G is a one-board solution which prevents this corrupted video by balancing the delays between the main and backup feeds. It can alternatively be used to manually switch to backup in non-emergency situations when equipment in the chain needs fixing or updating.

Safe Switch 3G’s clean switching comes from the full framestore synchronizer in each input stream which will ensure that both inputs to the switch are correctly timed to the external analogue reference resulting in no disruption. The synchronizers act as a self-adjusting delay, allowing a clean transition between the two channels even if their relative timing has slipped. Safe Switch 3G can even lose the reference signal and not affect the output. Loss of reference protection – where Safe Switch 3G will change its timing smoothly between the reference and the inputs, keeping the output valid at all times – is an unusual and technically-advanced feature which further extends the board’s primary purpose of protecting the output from any disruption.

Safe Switch 3G is also an intelligent switch. It constantly checks both of the inputs so that the output of the switch always remains proper and valid, and can be set to automatically switch away from the user-selected input if it does not meet the set requirements. It extracts information about various parts of the video signal to decide which of the two inputs is better, based on the engineer’s selection of which faults are significant. The 16 video and audio parameters which can be selected to perform a switch, and which are listed in order of priority, are input missing, input video standard incorrect, EDH missing, EDH full field error, EDH active picture error, line CRC error, audio group 1 missing, audio group 2 missing, audio group 3 missing, audio group 4 missing, active video black, active video frozen and audio silence in a selected group. With some processes – such as video compression or converting to analogue and back – introducing small changes frame-to-frame even if the input picture is frozen, the customer-requested processed frozen picture detection feature allows Safe Switch 3G to intelligently distinguish between this noise and real changes in the picture content – and so correctly flag up an error condition and auto switch. Safe Switch 3G will switch away from an error on the user-selected input only if the other input is free of that fault. If both inputs have different alarms, it will use the most significant alarm to decide which feed to select. Following a switch it can either reselect the main feed automatically or by user intervention.

In addition to the automatic switching, two fault indications – with their own list of chosen parameters – can also be set and assigned to GPIs if desired, allowing very flexible monitoring. Each fault indication can be assigned to a specific input, to either input, or to only become active if both inputs show a selected fault.

Explained Crystal Vision’s Managing Director, Philip Scofield: “The Safe Switch 3G was developed after specific requests from two large broadcasters in different parts of the world. Both broadcasters now use the Safe Switch 3G to give them confidence that they can manage failures in video, audio or reference signals and still meet their service level requirements that only allow a few minutes of downtime per year.”

Safe Switch 3G and Safe Switch-L 3G are both space-saving 100mm x 266mm modules which can be housed alongside any other products in the standard Crystal Vision frames – available in 4U, 2U, 1U and desk top box sizes. Up to 12 Safe Switch 3G modules or six of the ‘double decker’ Safe Switch-L 3G can fit in a 2U frame, with the Safe Switch-L 3G additionally providing a second feed of output B, input and reference loop-throughs, and extra GPI connections. Both boards include relay bypass protection on power failure or board removal, giving the system an extra layer of security and preventing signal loss. The Safe Switch 3G version can also include integrated fiber output connectivity by fitting the FOP fiber output option – ideal for when it is being used as the last point on the output of a studio with the signal needing to be sent over a long distance to the central router or station transmission output.

There is a choice of control options to suit all preferences. The Statesman PC control software can be used to either ignore or create an alarm on any of the fault conditions that Safe Switch 3G can measure. Also available are very flexible GPIs – ideal for GPI-focused broadcasters who want to have direct control of the board. The six GPIs on the Safe Switch 3G and 12 GPIs on the Safe Switch-L 3G are all bi-directional, allowing them to be configured as either GPI inputs or GPI outputs which gives flexibility when setting up buttons and lights for GPI control and monitoring of alarm conditions. Other control options include board edge switches, an active front panel on the frame, a remote control panel and SNMP.

Safe Switch 3G and Safe Switch-L 3G are both shipping now.

Based at Whittlesford near Cambridge in the UK and with an office in the USA, Crystal Vision provides digital keyers, picture storage modules and a full range of interface equipment including converters, synchronizers, distribution amplifiers and audio embedders to the professional broadcasting industry worldwide.