Canare video jackfields are “Western Electric” (also known as WECo) style, widely used worldwide, which use enclosed jack-pair modules with internal micro-switches. They pass uncompressed, 1080p HDTV video up to 3Gb/s (SMPTE424M).
To minimise dust and dirt ingress, the jack pairs are housed in rugged diecast aluminium clam-shell housings, and incorporate hermetically sealed, double reverse-action micro-switches mounted on a screened PCB and rated 30,000 operations. Two precision 75 ohm metal-film resistors offer near perfect signal-path termination. Jack modules are secured by front-panel screws, permitting simple module exchange. Modules have a manufacturer’s lifetime guarantee.
Two jack modules are available. DVJB-W is “normal through”, which provides a normalled route between top and bottom jacks. On inserting a patchcord plug into either top or bottom jack, the disconnected circuit is automatically terminated into a 75 ohm load. DVJB-S is “straight through”, which is effectively two single jacks in one housing, each terminated with a 75 ohm load until a jack plug is inserted. This module is useful for bringing up auxiliary equipment on a central jackfield location. From the front, the modules can be distinguished apart as the DVJB-S type have a slightly serrated jack ring. From the rear, DVJB-W are coded blue, DVJB-S are green.
Jackfields are available in 1U (high density format) in 2 x 20, 2 x 24 and 2 x 26 configurations, together with 2U (standard format) in 2 x 24 and 2 x 26. 2U types feature extra-large designation strip. Jackfields are supplied as standard either with DVJB-W or with DVJB-S modules, however component parts (front panels, jack modules) are available separately to enable users to make up mixed configuration panels. 2U Jackfields do not have lacing bars, but a kit for the 1U jackfields only may be ordered separately (stock code 48-359).
Suitable 75 ohm flexible patchcords VPC-WC are available in three lengths, using black cable as standard, and with black strain-relief sleeves on the connectors. Other lengths and colours are available to special order, subject to a minimum quantity of 10 pieces of each type.
Patchcord plug to BNC socket adapters BCJ-VWP are also available, to enable cables terminated with BNC plugs to be directly patched into the jackfield.
SMPTE 292M & 424M Standards
SMPTE 292M is a standard published by SMPTE which allows for bit-rates of 1.485 Gb/s, and 1.485/1.001 Gb/s. These bit-rates are sufficient for to transport uncompressed High Definition video. This standard is usually referred to as HD-SDI and is one of a number of standards that define a Serial Digital Interface based on a coaxial cable, intended to be used for the transport of uncompressed digital video and audio in a television studio environment. SMPTE 424M develops SMPTE292M allowing for bit-rates of 2.970 Gb/s and 2.970/1.001 Gb/s over a coaxial cable or connector panel. These bit-rates are sufficient for uncompressed 1080p video at 50 or 60 frames per second often referred to as 3G HDTV.
The stipulated interface condition (cable & connector) are:
SMPTE 292M - insertion loss 20dB or less at 750MHz - return loss 15dB or less at 1.5GHz.
SMPTE 424M - insertion loss 20dB or less at 1.5GHz - return loss 15dB or less at 1.5GHz and 10dB or less at 3.0GHz.
Note that although the MUSA and WECo systems are visually similar, they are not compatible with each other.