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I found this instrument at a garage sale a while back. It consists of two parts: a bent sheet metal housing with a stand near the front and rubber feet on the bottom; and an insert.

I haven’t been able to find a lot on it. The only clue I have is the manual for HP’s vacuum tube voltmeter model 410b that I bought with it. The plug on the back matches one of the accessories used with the voltmeter mentioned in the manual.

My initial thought was that it was an oscilloscope, by the front switches being label DB, instead of dB shot that theory out the window. I couldn’t find any units that looked like that since.

Can anyone help me out? I would be willing to answer any questions about interior items that I can.

front panel of instrument

Link to more images

Update: I just dismantled the instrument. I do think more concretely that it was a dBmV meter or a signal strength meter of some kind. The 4 Black rectangles turned out to be variable inductors. The three switches on the side of the front panel turned out to be toggling resistor filter for the top coaxial plug. The plug on the back is for AC current to recharge the batteries inside, since one of the lines from the plug leads to a diode and a “Ohmite”.

I would be willing to post pictures of the individual components if any want to see

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  • \$\begingroup\$ Why do you assume DB is not the same as dB? \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Jun 20, 2018 at 3:13
  • \$\begingroup\$ @immibis Why would a company miss label units? It makes no sense. Plus the batteries inside make me think otherwise also \$\endgroup\$
    – user3831093
    Commented Jun 20, 2018 at 3:18
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    \$\begingroup\$ @user3831093 But that’s kind of like saying they mislabeled “VOLT METER” because it’s in all-caps as well. It’s just the stencil they used. \$\endgroup\$
    – Blair Fonville
    Commented Jun 20, 2018 at 3:24
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    \$\begingroup\$ Well, it is not an oscilloscope. No screen for viewing the signal. DB or dB has nothing to do with that. \$\endgroup\$
    – JRE
    Commented Jun 20, 2018 at 5:59
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    \$\begingroup\$ I think it is a very old and crude selective level meter, input attenuator on the left, tuning controls on the right and meter in the middle. The monitor switch probably controls a resistive termination. \$\endgroup\$
    – Dan Mills
    Commented Jun 20, 2018 at 7:57

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If I had to compare to other pictures I found, I'd say that this is an old signal level meter. I came to this conclusion when I saw the "D.B.M.V." on the scale. So I looked up "old dBmV meter" on Google, I saw multiple devices that shared the same characteristics. Here's something that looks like it has the same functionalities.

You can find more devices from a website called, "Old CATV Equipment Museum" so that's where I'm basing my information from.

enter image description here

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  • \$\begingroup\$ Then why would it need a volt meter bypass? \$\endgroup\$
    – user3831093
    Commented Jun 20, 2018 at 3:35
  • \$\begingroup\$ Possibly to filter out some noise. That's a pure guess to be honest. \$\endgroup\$
    – user103380
    Commented Jun 20, 2018 at 3:41

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