Open Wire Artifacts Are Disappearing Daily!
Help us to preserve this amazing technology . . .
The public, non-profit mission of The Electric Orphanage’s Telecom Preservation Division, is to highlight artifact examples of the communications science by display, mobile exhibit and permanent protection. Commercial communications open wire materials are found in just a very few places in the United States today. As we speak, hundreds of miles of open wire railway signal aerial wire is being wrecked out with no thought to preservation.
It is the avowed directive of The Electric Orphanage to seek and preserve items material to the story of America’s open wire heritage. If you know of a line wrecking job or retirement of materials from any open wire operator, we want to know about it. Please contact us. Donations are also accepted so they may be utilized in this website for informational purposes. All items donated will receive public credit and never sold, re-sold or salvaged. They will always be guaranteed to remain with this public enterprise so that they may tell their story to others and reflect well upon those who participated in this grand undertaking. Help us to help you. We look forward to hearing from you!
In order to facilitate a better understanding of the open wire era, the artifacts pictured in every section (unless otherwise noted) are from the collection of The Electric Orphanage.
This is the external view of a Western Electric Biased Relay for use on open wire telegraph systems. Its voltage on the line side was 130 volts with variability built into the unit. It was removed from the AT&T – Lincoln Telephone & Telegraph Junction in 1956. The coil was 24 volts and the current flow was 60 miliamperes.
The case was made of a bakalite-type plastic black on the interior, but colored gray on the outside. It attached to the base by pushing down and then turning slightly to engage the two opposing pins in the slot afforded by the base design.
This unique device was one of hundreds employed along the transcontinental line and other major toll leads for telegraph operation. These were considered the early “plug-ins” of the electronics culture.
About the No. 255 Biased Relay
“Because relays are more sensitive receiving units than printer magnests, they generall are used iwht fixed station equipment to allow greater operating distances between machines. The relay used with the M-15 machine is a polar relay of the 215 or 255 (Western Electric Company) type. Each of the two windings in the 215 type has 85 ohms resistance and is designed for 60 ma of signaling current only. The windings of the 255 are 136 ohms each and can be used on 20 to 60 ma of signaling current. In addition, the 255 type has larged knurled pole piece locknuts which make it easier to adjust the pole pieces, and its contacts are of later design and better materials.”
“The magnet is a permanent magnet made of hard steel. The two yokes, armature, and the pole pieces are made of permalloy, which is a special allow that conducts magnetic lines of force in the same manner as soft iron. The relay armature is a thin spring clamped at its base. It can be flexed from the marking to the spacing contact but, because it is a spring, it stands midway between the pole pieces when no current flows in the winding. Magnetic lines of force pass from the north pole N of the permanent magnet, through the upper portion of the left yoke and the north pole piece, and across the left air gap of the armature. From the armature the magnetic lines of force pass across the right air gap, through the south pole piece and the upper portion of the right yoke to the south pole of the permanent magnet. Magnetic lines of force also pass from the north pole of the permanent magnet, through the lower portion of the left yoke, across the base of the armature at the point where it is clamped, and through the lower part of the right yoke to the south pole of the permanent magnet. The magnetic lines of force attempting to flow downward through the armature are of equal strength to the lines of force attempting to flow upward. Therefore, all lines of force in the armature are canceled, and the armature has no definite polarity. When current flows thorugh the winding in a direction to cause the lines of force in the armature to flow upward, making the top a north pole, the armature will be attracted by the marking pole piece since this pole piece is a south pole due to the permanent magnet. If the current flow is reversed, the polarity of the armature is reversed making the top a south pole which will be attracted by the spacing pole piece (north). When no current flows in the winding, the armature is centered between the two pole pieces since it has no polarity and the attraction to both pole pieces is equal.”
With A Teletypewriter
“When a 255 type relay is used as a line relay of a teletypewriter on a neutral circuit, the bias winding is locally supplied with 30 ma of steady current in a direciton to cause the armature to be held against the spacing contact. 60 ma of line current is passed through the line winding in a marking direction. When a marking impulse is transmitted, the magnetic field induced by the 60 ma of line current in the line winding overcomes the magnetic field induced by the 30 ma of locally supplied current in the bias winding. This causes the armature to move to the marking contact under the influence of an effective force of 30 ma of current through the line winding (60 minus 30). When a spacing impulse is transmtted, there is no current flow in the line winding and the armature is moved to the spacing contact by the 30 ma of current in the bias winding.”
This information was taken from the publication: Teletypewriter Circuits and Equipment (Fundamentals), U. S. Department of the Army Technical Manual, October 1947, Pp. 16-17, TM11-680 T.O. 16-1-117.