CCTV Siamese Cable (coax + power) - 100m roll

CCTV-SIAM-100M

One cable combining the video coax with a power pair, so a single run reaches each camera instead of two.

Type: Coaxial
Length: 100 m
Connectors: BNC / DC

In-depth technical details

This siamese cable's BNC end uses the 75ohm video/broadcast impedance standard, not the 50ohm RF/data standard -- mixing the two causes real signal loss from impedance mismatch. The DC barrel end's exact size and polarity are not confirmed in the catalog's spec data, and barrel size/polarity are not standardized across suppliers, so check the connected camera's power adapter before relying on it.

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End A

BNC

01 Centre conductor Carries the video signal — the copper wire at the very core of the coaxial cable.
02 Bayonet lock Push and give it a quarter turn to lock. That is what keeps a camera connected on a pole in the wind.
03 Braided shield The copper braid surrounds the core and holds the cable's impedance constant along the whole run (50 or 75 ohm, depending on the cable).
04 50Ω vs 75Ω BNC connectors come in two incompatible impedances: 50 ohm (RF/data standard) and 75 ohm (video/broadcast standard). Mixing them causes real signal loss (about 5% per mismatch point) — a common mistake when a 50 ohm BNC cable ends up on a 75 ohm CCTV run.
05 Strain-relief boot Stops the wires flexing where they leave the plug — the exact point most cables fail.
06 Outer jacket The outer sheath protecting the conductors inside from abrasion and moisture.

Technical illustration, not a photo of the actual product

End B

DC barrel plug

01 Inner pin Positive by the usual convention. Reversed polarity destroys a device instantly, so never assume compatibility from shape alone.
02 Outer barrel Negative. The barrel and pin diameters (5.5 × 2.1 mm, for example) are what actually decide whether it fits.
03 Strain-relief boot Stops the wires flexing where they leave the plug — the exact point most cables fail.
04 Outer jacket The outer sheath protecting the conductors inside from abrasion and moisture.

Technical illustration, not a photo of the actual product

How it works

Coaxial cable

The signal travels on the centre conductor and returns on the braid, and the spacing between them never changes along the cable. That constancy is what holds the 75-ohm impedance and stops reflections ghosting the picture.

01 Centre conductor A single copper wire carrying the whole signal.
02 Dielectric Foam insulation holding the core exactly central. Crush it and the impedance changes, and the picture suffers.
03 Shield A grounded conductive wrap that absorbs electromagnetic interference before it reaches the signal.
04 Outer jacket Protects everything inside mechanically. It plays no electrical role.

Technical illustration, not a photo of the actual product

From the published standard

How it works

A Siamese cable bundles two electrically independent cores inside one jacket: a 75-ohm coaxial core for video, and a separate two-conductor pair for power, run side by side but never connected to each other. That means pulling a single cable from the control room to the camera location instead of two, which is what actually saves installation time. At each end the two cores split apart again: the coaxial core terminates in a BNC connector for video, the power pair terminates in a DC plug — whose polarity must be checked before connecting, since reversing it can damage the camera.

Construction: 75-ohm video coax + separate DC power pair, one jacket
Termination: BNC (video) and DC plug (power), independent circuits
Benefit: One cable pull reaches the camera instead of two

This information comes from published sources about this type of product, not from the supplier.

Technical specifications

Type	Coaxial
Length	100 m
Connectors	BNC / DC

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