[BC] Xmitters at aol.com

[dhultsman5@aol.com]

Richard:
 
I have seen a many equalized telephone line, 5, 8, 15 kHz. (Audio) response  lines equalized by telephone techs and in all cases the line side was strapped 4:1 at the transmitt end and 125 ohms at the receive end with the equalizer strapped across t & R.    I have not been involved with the newer digital equalizers but all of the lines I was involved with under Bell Operating Companies always made used of the 125 Ohms toward the CO and from the CO.
 
Dave Hultsman
Broadcast Channel Manager
DRS - Continental Electronics .
Birmingham, AL
Tel Toll Free (888) 822-1078
Fax (205) 822-6441
 
 
-----Original Message-----
From: RichardBJohnson at comcast.net
To: broadcast at radiolists.net; broadcast at radiolists.net
Cc: K7qa at aol.com
Sent: Tue, 10 Apr 2007 8:02 AM
Subject: Re: [BC] Xmitters at aol.com



The impedance of various telephone cables is well documented. 16-gauge 
spiral-four toll entrance cable is 540 ohms -j460, 22 AWG emergency cable is 464 
ohms -j449, paper insulated (inter-city toll cable) is 910 ohms for 26 AWG, 22 
AWG is 756 ohms, 19 AWG is 453 ohms, 16 AWG  is 320. All from Page 823, Wire 
Transmission, Reference Data for Radio Engineers, fourth edition. Nothing is 
close to 150 ohms. It is well known that the series 500 "standard black 
telephone" was called the "500" because its hybrid (anti sidetone network) was 
designed
for 500 ohms. Historically, the telephone lines have been called "500 ohm" 
circuits.

Also, there are no 300-ohm windings on a 111-C. The transformer consists of four 
identical windings that are electrostatically shielded so they can be connected 
in any manner. The usual (read correct) connection is for two windings to be 
series-connected for the output, and two windings to be series-connected for the 
output.

See http://www.oldradio.com/current/111c.html , It shows the two usual methods 
of connection. Note that both the line-side and the drop side can be connected 
either in series or parallel. Don't be fooled by the "typical use" note. It's 
for "short" i.e., unequalized circuits.

I would guess that your response was either a test to see if I was still awake, 
or not very well thought out!

--
Cheers,
Richard B. Johnson
Read about my book
http://www.AbominableFirebug.com


 -------------- Original message ----------------------
From: K7qa at aol.com
>  
> In a message dated 4/9/2007 6:41:47 AM Pacific Daylight Time,  
> RichardBJohnson at comcast.net writes:
> 
> The  circuit feeding the telco pair should not be connected as 150 ohms  
> unless
> there has been a problem obtaining the required frequency response.  
> 
> 
> Most standard balanced telco multiconductor trunk lines used for many years  
> had an internal surge impedance of 135 to 150 ohms at audio frequencies. The  
> 111C had individual 300 ohm windings for a good reason.  Connect the  111C 
> transformer split windings in parallel to achieve 150 ohms on the line side  
and 
> in series for the 600 ohm equipment side. 
>  
> tm
> 
> 
> 
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