In the picture below, I have a power resistor, which is powered either from 12VDC or 24VAC from the rest circuit, as well as another component, which is inserted on the one cable leading to the resistor.

enter image description here

My questions are:

  1. What does each number mean on the power resistor marking?

  2. What could the other component be?

Edit: This is a CCTV camera and the power resistor is used to make sure, through heating, that the glass in front of the lens does not become foggy.

  • \$\begingroup\$ It would be a help to know what the function of the circuit is. Please edit into your question. \$\endgroup\$
    – Transistor
    Jan 25, 2021 at 14:27

2 Answers 2


The "gold" metal clad power resistor is made by: -

S.I.R. SOCIETÀ ITALIANA RESISTOR, Via Isonzo 13, 21053 Castellanza (VA), Italy

The general data sheet that describes their metal clad products is HERE and that particular resistor is 68 Ω 25 watts: -

enter image description here

The other component looks like a ferrite core of some sort. The "15" might indicate it has an inductance of 15 μH.

Good luck.

  • \$\begingroup\$ Any information about the difference between RH, RHS and NH power resistor types? \$\endgroup\$
    – NickG
    Jan 25, 2021 at 18:43
  • \$\begingroup\$ @NickG your best bet is to go onto the website for SIR and find out yourself - if the website doesn't tell you then contact SIR. If there's something you don't understand about them, link the datasheet. \$\endgroup\$
    – Andy aka
    Jan 25, 2021 at 18:47

The resistor is manufactured by SIR, and is of type RHS25. This is a 25W aluminium housed wire-wound resistor.

The 68R J indicates the resistance and tolerance, that is a 68 Ohm resistor with 5% tolerance.

1999 is a date code of manufacture, with the first two digits most likely being week in year, and the second two being the year itself, so from May 10th 1999 to May 16th 1999.

The second component is most likely an inductor, but it could also be a capacitor. Hard to tell without removing the heat-shrink tubing.

  • \$\begingroup\$ Thank you for the information. Could you please also explain the difference between rh, rhs and nh resistors? \$\endgroup\$
    – NickG
    Jan 25, 2021 at 10:06

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