[GreenKeys] Northern Radio Volume and Current Indicator...

Wed Nov 23 15:31:34 EST 2016

    The paper introducing the Volume Indicator and Volume Unit is at:
http://www.aes.org/aeshc/pdf/chinn_a-new-svi.pdf

    The paper originally appeared in the Journal of the IRE but was 
reprinted in many places.
    The meter was developed mainly by AT&T because previously there was 
no standard for either transmission levels or means of measuring it. 
AT&T found they had a hard time getting agreement on levels from sources 
and destinations of broadcast lines.  The meter is designed to give a 
reasonable visual indication of loudness of speech and music but needs 
to be used with some understanding of what it does not show, i.e. peaks. 
The assumption when using a standard VI on speech or music was that the 
actual peak was about 6 to 10 db higher than the meter showed.
    The standard VI has tightly specified ballistic and electrical 
response characteristics. It has a shaped magnetic structure to give a 
more nearly logrhymic scale charisteric. The original specs also 
addressed the scale design and color. A meter meeting the original specs 
does not have a manufacturer's name featured on the front.
     There were two scales, A and B, one with the Db or VU scale on top, 
one with the percentage scale on top. Otherwise the same.
     The basic sensitivity is 0 = 1 mW in 600 ohms but the rectifier in 
the meter creates some harmonic distortion on the line its connected to 
so normally its used with a pad. In the usual broadcast plant the zero 
level was 8db above one milliwatt. This box uses an electronic amplifier 
probably partially to eliminate the distortion but also be make possible 
the reading of lower level signals.
     The reference level of zero indicated VU = +8 VU on the line is of 
historical origin. The first repeater amplifiers used by AT&T had an 
overload point such that with a margin for peaks an operating level of 
6mW in 500 ohms was established. This is nearly identical to the +8 VU 
in 600 ohms used for the meter. So, different facilities has only to 
change the meters  in order to meet the new standard, there was no 
significant change in transmission levels.
     The meters were made by all the manufacturers of high quality 
meters such as Weston. I don't remember if the AT&T standard required 
illumination but most meters are illuminated with the lamps placed to 
minimize shadowing. Also, the original meters had spade shaped pointers.
More than you ever wanted to know.
    Some years ago the BBC introduced a peak reading meter. This was 
adopted especially by recording studios but has a set of vices all its 
own. Modern indicators, which are electronic, show a combination of the 
VI indication and a peak indicator.

On 11/23/2016 8:53 AM, Roy Morgan wrote:
> Eugene,
>
> That VU meter on your new gadget is a kind of a treasure - it appears to
> be a high quality Simpson GEn You Wine VU meter.  Not easy to find and
> especially precious in the world of audio.
>
> The official organizaitons involved in audio work (RIAA and others)
> published the official standard for such meters in the 30's or 40's.
> That is NOT a normal milliammeter with a rectifier on the back!
>
> I can provide further details once I get to my archive of informtion.
> Email me if you are interested.
>
> The thing you have appears to accept audio signals and convert them to
> some sort of signalling voltages - perhaps for transmission over FAX
> circuits or radio broadcasts.
>
> (I have not seen he manual yet.)
>
>
> On Tue, Nov 22, 2016 at 12:36 PM, W2HX <w2hx at w2hx.com
> <mailto:w2hx at w2hx.com>> wrote:
>
>     Hi guys,____
>
>     __ __
>
>     I picked this up on ebay recently. I found a manual online
>     (available from the link below). It says the following, “The
>     Northern Radio Volume & Current Level Indicator, Type 254 is used as
>     a signal level and loop current indicator at both transmitting and
>     receiving terminals.”____
>
>     __ __
>
>     http://w2hx.com/x/NorthernRadio/Type254Model1/
>     <http://w2hx.com/x/NorthernRadio/Type254Model1/>____
>
>     __ __
>
>     Anyone ever play with one of these? Maybe someone used it while they
>     were in active use? ____
>
>     __ __
>
>     Should look nice next to my Type 152 tone converter____
>
>     http://w2hx.com/x/NorthernRadio/Type152Mod2/
>     <http://w2hx.com/x/NorthernRadio/Type152Mod2/>____
>
>     __ __
>
>     __ __
>
>     Thanks____
>
>     Eugene W2HX____
>
>     __ __
>
>
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> Regards,
> Roy
>
> Roy Morgan
> k1lky since 1958
>
>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL