How do you Determine if a SC 1212 is wired for metallic or straight line ringing

[RotoTech99]

For a Stromberg 1212 or similar set, how do you determine if it is wired for metallic or straight-line ringing?

(Assuming the ringer used is a SC 55A straight line, or 56A straight line biased ringer operating on a 20 Hz,
straight ringing line providing 45- 108 VAC)..

What also would the proper connections be for the ringer for metallic or straight-line ringing?

[Ktownphoneco]

RT99    ....  I've attached a schematic showing the various methods for bridged ringing, party (tip / ring) etc., etc..     Bridged ringing is at the very top of the page.     You may want to print the page, as it's a lot easier to read.

Jeff Lamb

[unbeldi]

A metallic circuit is defined as a circuit that does not use a ground (earth) return, but consists entirely of metal conductors. This would primarily be a two-wire line. Metallic ringing (signaling) therefore occurs entirely over the metal conductors.

Metallic circuits are contrasted by the ground-return circuit, or simply called grounded line, in which the return conductor for electricity is formed by connection to a good earth connection in the central office as well as at the substation.

The definition of straight-line ringing is independent of the type of circuit used for signaling. A straight-line ringer may be used on both types of lines, grounded or metallic.  A straight-line ringer responds to a wide frequency range, typically 16 to perhaps 40 Hz or even higher, as contrasted with a frequency-selective ringer which responds only to a very narrow range of frequency, perhaps less than 10 Hz in width.  Frequency-selective ringers may be recognized by their physical construction combined with some experience.

Both types, straight-line and frequency-selective ringers, may be used on metallic or ground-return local loops.

So, the way you phrased your question does not present a proper choice that can be answered one way or another.
However, you may recognize metallic ringing, when the ringer (including its condenser) is not connected to a ground, but between the two conductors for speech, TIP and RING.  Grounded ringing, also called divided ringing, happens over one of the speech conductors and ground as the return for the ringing current.

In the very early days of telephony, a grounded line consisted of only one wire; speech and signaling was transmitted over the same wire using the earth connection as the return. But later, when all speech was conducted metallically over two wires, a grounded line used the earth connection as a third conductor for ringing, and other forms of signaling, only.

[RotoTech99]

Dear Unibeldi:

The good news is my 1212 rings using a SC 56A straight line biased ringer.

The reason for my earlier question was based on the modern single line service that most call bridged ringing that is typically 20 Hz. @ 45-108 VAC.

I am using a 3 conductor cord connected to as follows: GREEN (L1) wire on G, RED (L2) wire to F, and my YELLOW (Gnd) on H... Would that be grounded single line ringing?

[unbeldi]

I am using a 3 conductor cord connected to as follows: GREEN (L1) wire on G, RED (L2) wire to F, and my YELLOW (Gnd) on H... Would that be grounded single line ringing?

From the perspective of your telephone set, yes, it would be.

However, from the perspective of the modern telephone line it is still metallic ringing, as the ringing signal from the central office uses the two line wires.  You can leave your set as wired originally with three conductors in the mounting cord, but you need to connect the third, yellow wire at the wall jack or terminal board to that side of the line that is not already connected to the other side of the ringer in the telephone.  Which one that is depends on the polarity that is wired inside the phone, and you need to trace it, or simply perform the experiment of moving the yellow wire between L1 and L2 while the line is ringing.

If your line comes from a central office, and not from VOIP telephone adapter, one of the two line wires (TIP) is most likely actually connected to earth ground,  but this only serves to minimize wire corrosion.

[RotoTech99]

 Just so you know, I've been using 3 wire line cords with my antique sets out of habit because I ran across one that wouldn't ring without the ground wire on one of the ringer connections.

I think you answered my question, Thanks, I will try to remember what you told me.

I also find that when using cord restraints original to the set, the extra width of the 3 or 4 conductor spade to modular line gives the cord restraint more to grip, and avoid accidental yank-out.