US2140673A - Telegraph system - Google Patents

Description

Dec. 20, i1938. M. L. GREENE ET A1.

TELEGRAPH 4SYSTEM Filed Jan. 1957 Ell ML- cRff/VE mLn/foAas/e.

A TTORNE V Patented Dec. 20, 1938 UNITED s-'mrlazsI PATENT OFFICE TELEGRAPH SYSTEM.

ofNew York Application January 29, 1937, Serial. No.- 123,064

2 Claims.

This inventionr relates to a telegraph system, and more particularly to a system for transmit-v ting telegraph signal pulses over along. telegraph.

proved telegraph circuits and. arrangementsy which require less adjustment and maintenance at the outlying station. Y

Another object ofthis invention is to vprovide a telegraph system which requires no changes in the` adjustments of the apparatus at the outlying station With changes in the leakage resistance of the line due to weather changes.

Stillanother object of this invention relates to a telegraph system in which the polarized receiving relays are p-rovided at each end of the line; These receiving relays do not require any mechanical or electrical bias under. normalor dry Weather conditions.

These and otherv objects and features of the invention can be more readily understood from `the iollowingf description when read with reference to the attached drawinginwhich isshovvn graph leg of a composite toll line, andinclude.

the usual terminal and intermediatev com-.- posite sets. Line I6 may also be either an open wire line or a cable circuit, ora portion of itmay include open wire lines and other portions cable conductors.

The usual noise suppression filter units may also be included. These noise' suppression units.

' have not been shown becauseA they operate in their usual and normal manner which is well understood so that further description of them would only needlessly complicate the description and tend to obscure this invention.

At the outlying station B, the receiving polarized relay Il is connected directly in series with line IB. The line circuit is then connected to the its marking contact. Polarized relay. Il operates This telegraph channel may be an.

receivingldevice l2. Receiving device l2 may be of any suitable type, `as for example a telegraph sounder or printing magnet of a teletypewriter.

'I'he transmitting relay i3 is controlled from the contacts 30 of the transmitting device at the outlying station B. Transmitting device 3G may be of any suitable type, as for example atelcgraph key, contacts of a tape transmitter or of a teletypewriter keyboard. The current iiowing through the upper or biasing winding of the transmitting'relay i3 is in such a direction as to tend to move the armature to the spacing contact. The current iiowing through'the lower winding of sending` relay i3 when the transmitting contacts Sill are closed, tends to move the armature ofl relay i3 to its marking contact. This current owing through the lower winding of sending relay |3` causes a magnetic eiiect upon the relay armature which overcomes the magnetic effect of the upper biasing winding. In the preferred embodiment both windings or relay i3 are the saine while the' current throughthe lower winding whencontacts 3d are closed is twice the current Iiowing through the upper winding: This causesv the relay to move to and remain upon its marking contact so long as transmitting contacts 3Q., remain closed, However, when contacts 3i! are vopen in accordance with the signal pulses to be transmitted, the current flowing through the lower'winding of the sending relay I3 falls to zero at which time the current owing through the upper or biasing winding causes the armature to Amove to vits spacing position and connect the postive 13D-volt. battery to the line circuit. Thus, the sending relay I3 connects ground and positive 130volts to line-lil` through the Winding of receiving. relay l l in accordance with the signal'ipulses. transmitted from station B.

At station A, line lll is connected to the armature ci polarized relay I 6. Positive 65 volts is connected to the marking contact of relay I6 through the lower winding of the polarized receiving relay i3. Negative 65 volts is connected to the spacing Contact of relay i6. Receiving relay i831 is provided with an upper winding which is normally short-circuited by break relay Il. Relays i, Il and |8-are shown connected to a local subscribers line circuit.

It is to be understood that they may comprise relays of any suitable line circuit or repeater, including carrier current repeaters, duplex repeaters or single line repeaters. As shown, receiving relay lretransmitssignals received from line lil to ther subscribersstation 2'4- over line 25'in a mannerwell .understood-in the priorart and need not be described herein. In addition, polarized relay I6 repeats the signal impulses received from subscribers station 24 in the usual manner so that this also need not be described in detail. However, the break relay Il provides a circuit for controlling the locking of upper winding of relay I8. When the attendant at the subscribers station 24 transmits a break signal during the time signal station 24 transmits a spacing signal it will cause the sending relay I5 and the break relay Il to move to their spacing positions if the armature of relay IS is in its marking position. When break relay Il leaves its marking contact it removes a short circuit from the upper or locking winding of the receiving relay I3, which causes current to flow through the locking winding of relay I8. This current is in such a direction as to maintain this relay on its marking contact. This insures the proper transmission of the spacing signal to the lines Il) by preventing the armature of relay I6 from leaving the spacing Contact. Relay Il also functions in the above manner during long spacing or break signals transmitted from station 24 and insures the proper transmission o these signals to line I@ independently of any impulses which may be transmitted from station B over line i6. This insures the reception of the break signal at station B.

During the time signal pulses are being transmitted from subscribers station 25, positive and negative potentials or 65 volts are connected to line I by the sending relay I@ in accordance with the pulses transmitted. During this time the transmitting contacts 30 at station B normally vremain closed so that the line circuit Ill is normally connected to ground I5. Under these conditions, positive and negative potentials connected to line I0 by relay I6 at station A cause positive and negative currents to flow over line lil and through relay I I to ground I .at station B. Since the positive and negative potentials connected to line I0 at station A are substantially equal and opposite, they will cause substantially equal and opposite currents to flow in line ID. These currents operate receiving polarized relay l l equally in both directions, in the absence of any bias, as shown and described. In addition any leakage current will aiect both the positive and negative current received by relay Ii at station B in substantially the same manner so that the adjustment of this relay need not be altered to compensate for changes in the leakage resistance of the line. Thus, the bias of the signals received at station B is substantially independent of any leakage resistance of the line.

The term bias as applied to the received signals indicates a lengthening of one signal impulse and the shortening of another signal impulse; for example, marking bias means that the marking signal impulses are lengthened while the spacing signal impulses are correspondingly shortened, Whereas spacing bias means that the spacing signal impulses are lengthened and the marking signal impulses are correspondingly shortened. Thus the greater the bias of the signals, the less satisfactory they are for operating telegraph apparatus and relays, while the less bias, the better the quality of the signal impulses.

The common cause of this lengthening and shortening of the various signals is that marking and spacing currents are unequal; for example, for marking bias, the marking current is greater than the spacing whereas for spacing bias, the spacing current is greater than the marking current. These unequal currents cause the receiving relay to respond differently to the two conditions and thus add bias to the signal pulses. However, as pointed out above, the receiving relay II at station B receives substantially equal positive and negative currents representing the marking and spacing signaling conditions independently of the line leakage. Consequently, the receiving relay I I does not introduce any bias in the received signals and does not require any changes in the adjustment of the relay to compensate for changes of the line leakage.

The terms marking and spacing as used in this specication diierentiate two line or signaling conditions transmitted between the telegraph stations. The term marking is used to designate the line or signaling condition employed during the time no signal impulses are being transmitted, but the system is energized ready to transmit signal impulses. The term spacing designates the other signal or line condition.

When a spacing impulse is transmitted from station B the armature of the sending relay I3 at station B connects a potential of positive 130 volts to line lil. At this time the sending relay I6 at station A is normally maintained on its marking contact so that positive 65 volts is connected to line I at station A. 130-volt positive potential connected to line I0 at station B is substantially twice as great as the 65-volt positive potential connected to the line at station A, vand consequently causes substantially equal but opposite current to ow over line I0. This current is substantially the same as flows over line I0 during the time the armature of the sending relay I3 at station B is in its marking position and the armature of relay I8 at station A is in its spacing position. This reversed current causes the armature of the receiving relay I I at station B to move to its spacing position, and thus repeat the transmitted signals to the receiving device I2 to record a home copy. Since during the time signals are being transmitted from station B, the sending relay I6 at station A is maintained on its marking contact, the receiving relay I8 at station A will follow the current reversals transmitted over line I() and repeat the signal impulses to subscribers station 24 over line 25.

As pointed out above, with the potential connected to the spacing contact of relay I3 at station B substantially twice the potential connected to the marking contact of relay I6 at station A, the marking and spacing currents flowing in line Iii during the transmission of signal impulses from station B will be substantially equal in magnitude but opposite in polarity. Consequently, no mechanical or electrical bias is required for the receiving relay I8 at station A under this condition.

The foregoing description describes one specific embodiment of this invention, the scope of which is set forth in the following claims.

What is claimed is:

l. In a telegraph system, a line, a polarized relay associated with each of the ends of said line and responsive to reversals of current thereover, a transmitting device associated with each end of said line, each device having a spacing and a marking contact, a rst source of current or" one polarity and one potential associated with the spacing contact oi the first of said devices, a second source of current or opposite polarity and different potential associated with the spacing contact of the second of said devices, a third source of current equal in potential, but opposite in polarity to said rst source associated with the marking contact of said rst device through the operating Winding of the relay with Which said device is associated, and a source of ground potential associated with the marking contact of said second device, the relative potentials of said sources being such that the flow of current in each direction over said line is substantially equal when the marking contact of either device is held closed and the other device is operated to close either its spacing or marking contact.

2. In a telegraph system, a line, a polarized relay associated with each of the ends of said line and responsive to reversals of current thereover, a transmitting device associated with each of said relays, each device having a spacing and .a marking contact, sources of current of equal potential and of opposite polarities asscciated with the spacing and marking contacts of one of said devices, one of said sources being associated with one of said contacts through the operating winding of the relay with which said device is associated, a source of current or" different potential associated With the spacing contact of the other of said devices, and a source of ground potential associated with the marking contact of said other of said devices.

MONTE LEE GREENE.

WILLIAM LOCKWOOD RHOADS, SR.

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