VG-737 Video sync loss detector available from IRT Electronics is used to indicate the presence of a video signal by detecting the vertical sync component of a composite video signal. The detection circuitry used ensures that noise alone will not trigger the detector.
The video input is a high impedance bridging differential input circuit with the input common raised above ground, this allows the VG-737 input to bridge a signal cable without affecting common mode rejection circuitry that may be incorporated in the equipment terminating the cable.
The video signal level threshold at which the VG-737 video sync loss detector switches is set by an internal control and may be adjusted for a signal level in the range 0.4 V to 0.7 Vp-p at the input.
The video sync loss detector circuitry consists of a sync separator and vertical integrator which trigger a dual mono stable circuit that allows the response time of the alarm circuit to be set.
The response time is set by means of dip switches in the RC timing circuit and is adjustable from 1 to 32 seconds for the Video Fail time out and 1 to 8 seconds for the Video On response time, the adjustment being made in 1 second steps.
The alarm circuitry of the video sync loss detector consists of a latching circuit triggered by the detector circuit, which drives a relay whose contacts are available at the rear panel of the VG-737.
The alarm circuit of the video sync loss detector can be reset automatically upon return of the video signal or by a contact closure from the front panel or a remote circuit.
Visual indication of the state of the VG-737 detector and alarm circuits is provided by LED indicators on the front panel.
- Differential loop through input does not effect other equipment
- Good noise immunity
- Selectable alarm on and off timing
- Automatic, manual or remote reset
- 2 x Relay contact alarm outputs
- Convenient Eurocard design