VX-4026 - Universal relay switching Eurocards


VX-4026 Universal Relay Switching Cards are configurable, programmable Eurocard modules suitable for routing broadcast audio, video and control signals. With a copper path from the input connector to the output, the cards may safely be used in the broadcast transmission chain and frequently form part of automatic transmission backup systems. High quality DPDT sealed relays with Ag/Au-clad contacts (conforming to FCC Part 68) are used to ensure noise-free fast changeover between programme signals.

Programmable Logic Arrays (PALs) provide each relay with its control signal to operate or release. The VX-4026 card is configured so that these signals are derived from logical combinations of the control inputs and status signals from the relays themselves. This flexibility and reliability of control does not use microprocessor or real-time software, and makes system design and rack/control panel cabling very straightforward. It also minimizes the number of relays required to perform quite complex operations, in turn reducing the number of relays through which the signal must pass. Relay status is derived from the drivers themselves, and is brought to the edge connector (as well as to the front-of-board status LEDs on the eight-relay model VX-4026-1).

Model VX-4026-1 has up to 8 on-board relays with full access to all contacts on all relays, which is useful for changeover switching and alarm monitoring systems. Model VX-4026-2 has two banks of 8 relays, the second bank operating as a slave 1 from 8 selection with separate control, suitable for matrix switching applications where space and cost may be at a premium.


The signal paths themselves are arranged for flexible configuration. By using on-board links, a pair of contacts from each of the relays can be bussed together providing, for instance, source selection and matrix switching applications. Relays may be bussed together in groups of varying sizes, accommodating a video and audio bus on a single card. For larger matrices, several cards can be cascaded.

Resistors installed on the PCB can be used to terminate inputs that are not switched through to the output bus, which is particularly important for video switching, whilst on-board series distribution resistors can be used for audio applications. Signal routes are carefully impedance-matched and screened by a groundplane giving excellent transmission and crosstalk performance.

Card Format 220x100mm Eurocard
Audio Bandwidth 20Hz-20kHz ±0.2dB
Audio Crosstalk Better than -90dB @ 14kHz
Video Bandwidth 6MHz - 0.2dB
Video Crosstalk Better than -50dB @ 4.43MHz
Operating Time 7ms, bounce approx 0.3ms
Release Time 3ms, bounce approx 1.5ms
Relays 5V, 12V or 24V
Maximum Number Per Card 8 (VX-4026-1) or 16 (VX-4026-2)
PAL equations One per relay
Maximum Array Size 48x48