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When the government decided to more intimately control the telephone
business, they issued a decree which said that the phone companies of the United States could no longer decide that they alone
would supply the equipment which the customer could use on the companies' lines. The government said that, within certain
standards, anyone could put any kind of device on the phone companies' lines that they pleased.
However, that being done, it had to be noted that you could only put
so many phones on a given line and beyond that number, the phones simply would not ring, or, worse the ringing would stop
and the calling party would hear nothing. So, the phone companies came up with a standard. The Ringer Equivalency
Number, or, REN.
REN - Ringer Equivalency Number
The parameters for a standard of measurement for an REN became the
electrical characteristics of a standard Bell System telephone ringer circuit at the time. Beyond five ringer circuits
on the line, the phones might not ring. A number of things influenced this - the distance from the phone company Central
Office (CO) and the condition of the line itself (shorts, grounds, crosses, unbalances).
But, in general, a line with five phones on it should still ring even
at the farthest distance from the CO. So a standard Bell System phone had a ringer equivalence value of 1. As
manufacturers of telephone equipment made more equipment available to the market place, they included the REN on their products.
This included more than just telephones; it also included fax machines, external ringers and other signaling devices and the
like. The RENs on these devices could not, collectively, add up to more than 5 or there might be problems with
the telephones ringing.
Even before the REN standard came out, we often had to go out and disconnect
the ringer circuits in certain telephones when the customer had more than 4 extension phones on his line and he was having
problems getting incoming calls.
And that basically covers the REN.
Half-Ringer Network
With the advent of modular plugs and jacks, a problem arose for the phone
companies. Prior to modular, when a customer reported trouble on his phone line, the phone company test center would
perform tests on the line in question to "see" if it looked normal. One of the things the tester looked for was how
many telephones were on the customer's line. This was determined by how many phone ringers the tester "saw" on the line.
Inside the ringer circuit of each telephone is a big capacitor.
A capacitor (some call it a "condenser") is a device which has the ability to hold an electrical charge when a direct
current (DC) source was connected to it. By putting a meter inline with the capacitor and the source and then reversing
the polarity of the DC source, the capacitor will discharge through the meter which will cause the meter needle to rise, or,
kick, to a certain level and then drop back to zero. Each succeeding phone on the line adds to this reading and
the needle moves correspondingly higher with each bell circuit capacitor on the line so that the tester can "see" exactly
how many phones are on the customer's line.
Conversely, if there are no phones plugged in, there will be only a minimum
kick on the meter as the copper wire of the line to the customer's premises also has a certain ability to hold a charge as
well, but, nowhere near what a capacitor does. In this way, the tester can tell if the line tests okay or if it is open
- open meaning there is not a complete circuit through the bell circuit of a telephone.
Essentially, with the divestiture of the phone company in 1984, the company
no longer maintained the phone service up to the telephone equipment itself. This brought in the Telephone Network Interface
(NI) mentioned elsewhere in these pages. The phone company was now only responsible for the phone line up to the
NI and not the inside wire, the jacks or the telephone equipment on the premises, which were now the responsibility of the
customer to maintain.
Now this created a problem for the phone company. What if a customer
unplugged all their phones from the phone line? The line would still be okay to the NI but at that time the testing
equipment was not sophisticated enough to be able to determine whether or not it actually was okay to the interface.
So what to do because they didn't want to incur the cost of sending a repairman out on a wild goose chase?
Enter the Half-Ringer Network.
The Half-Ringer Network is a device which has the electrical attributes
of half the electrical value of a standard Bell System telephone ringer circuit. Here are two examples of these.
The first of these was a circuit board, like the one below, which
was connected across the line, that is, across the tip and ring, usually at the lightning protector in the phone company
side of the NI. The orange thingy is the capacitor; the other things are resistors, diodes and other semi-conductor
stuff and all these things together are what make it a network. This type device could have been wired directly
to the protector or to a small screw strip in the interface.
In later model NIs, these circuit boards were actually wired into
the module on the customer side of the NI. This module is the device which has the inside wire (IW) from the customer's
premises attached to it. This kind of module is shown in this picture below with the half-ringer board highlighted.
The picture below show the inside of a typical NI. Typically, you
will not be able to open the phone company's side of the NI unless you have a special Allen wrench.
On the left are the lightning protectors, the customer wire modules to
the right. The metal strip below the NI is the ground bus for the protectors and to which voltage from a hit on the
phone line is bled off. Your NI may vary in size and configuration but it should have all the elements contained within
as with this one.
As of 2005 the ability to test phone lines has become quite sophisticated,
so much so that a lot of phone companies do not need these half-ringer networks in the NIs any longer. And, in fact,
these devices can actually cause problems with certain types of lines and circuits and the phone companies often routinely
remove them on their visits to their customers' premises.
And, that about covers Half-Ringer Networks also.
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