US2383908A - Radio telephone system - Google Patents

Description

Aug. 28, 1945. I BQWERS 2,383,908

RADIO TELEPHONE SYSTEM Filed Feb. 5, 1944 5126/0 Station La" d ditation V V INVENTOR ./l. i. flowers A 'I'ORNE Y Patented Aug. 28, 1945 UNITED STATES searcn PATENT OFFICE RADIO TELEPHONE SYSTEM Albert Franklin Bowers, Charleston, W. Va., as-

signor to American Telephone and Telegraph Company, a corporation of New York Application February 5, 1944, Serial No. 521,228

14 Claims.

This invention relates to radio systems, and particularly to radio telephone systems adapted for communication between ships and points ashore.

One of the problems in such a system is that of transmitting between stations signals incidental to the establishment of telephone communication between a ship and a shore station, or between two ships.

In my prior U. S. Patent No. 2,265,056, granted to me December 2, 1941, I disclosed a system by means of which signals could be transmitted between a ship and a shore station by utilizing the carrier as a signaling medium This signaling method depended on the fact that when two stations such as a ship station and a shore station were in communication two carriers were used, although not simultaneously. One carrier frequency was used in talking from the shore station transmitter to the ship receiver, and a different carrier frequency was employed for talking from the ship transmitter to the shore receiver. When communicating in one direction the carrier in the opposite direction was cut off, and when both stations were idle neither carrier was transmitted. Therefore an operator at one station could operate a signal at another station by merely transmitting the carrier to such other station, and could operate another signal by cutting off the carrier.

Such a method of signaling is subject to the disadvantage that static or other interference in the carrier range of one of the channels employed might cause false operation of a signal. To overcome this ditliculty I disclosed in my patent above referred to an arrangement for operating the signal by interrupting the carrier by code pulses. For example, by interrupting the ship-shore carrier frequency at the ship station by dial pulses, a two digit code could be sent out. This actuated the codan relay (i. e. the anti-noise carrier operated relay) at the shore receiver, and this in turn actuated a step-by-step connector switch to complete the signal circuit. By using different codes the connector switch could perform various functions at the will of the ship operator, such as lighting switchboard lamps and ringing gongs at the shore station. Moreover, the lights and gongs would not respond to miscellaneous interfering signals picked up by the shore station receiver.

However, a system of the type above described has a number of limitations, especially where the system is used by vessels passing along a shore line. In such a situation each of several vessels must be able to communicate with any one of several land stations located along the shore. Usually a ship communicates with the nearest land station, but as it moves along shore it becomes necessary to shift its communications to the next land station into whose zone it enters. Moreover each shore station must be assigned two individual frequencies, one for transmitting and the other for receiving, and the frequencies assigned to any given shore station must be different from those of all other shore stations within communication range. Consequently each ship must be equipped with tuning crystals or other selective devices corresponding to the frequencies of the various shore stations with which it may have occasion to communicate. Due to these conditions it is evident that a ship operator, before he can communicate with a shore station, must manipulate certain switches by hand, or perform other manual operations which will tune his transmitter and receiver to the frequencies of a particular shore station.

Since each shore station is assigned individual transmitting and receiving frequencies which differ from station to station, communication cannot be established from shore to ship unless the ship receiver is in tune with a particular shore stations transmitting frequency. Consequently it follows that the operator on a ship proceeding along a coast line must shift his receiving fre- 30 quency as he leaves the zone of one shore station and enters that of another.

Calls originating on land must be relayed through a shore station to a ship. Indeed any one of several shore stations may have calls routed through it for a particular ship. It will be clear from what has been said above that no such calls can be relayed to the called ship unless transmitted at the frequency to which the shi stations receiver happens to be set at the moment. As ship stations usually keep their receivers tuned to one of the shore frequencies, it is difiicult for any other shore station to communicate with such a ship. For the same reason it is difficult for another ship to communicate with a ship whose receiver is so set, without first sending the message to the shore station to which the called ship is tuned, and then relaying the message to the ship through the shore station.

In order to overcome the foregoing difficulties it is herein proposed to make certain improvements in the type of signaling system disclosed in my Patent No. 2,265,056 above referre to, for the purpose of enabling signaling to take place from shore to ship or from ship to ship without being 55 subject to the limitations above discussed. The

improved system is of such character that it is not only useful in ship communication, but is adaptable for use in aviation for communicating between airplanes, or between an airplane and ground. It may also be used for radio control of various kinds of mechanical devices, or for communication between moving vehicles, or between a moving vehicle and a fixed station of any kind.

To accomplish these results it is proposed to establish a single carrier frequency common to all of the stations of a particular classification, such for example as coastal harbor stations. This frequency is to be used by the various ship and shore stations alike for dialing purposes only, and will be hereinafter referred to as the dialing frequency. By dialing this common frequency various signaling or control functions may be performed.

It is further proposed that all ship stations have their receivers modified to permit selective control of the various crystals or other tuning devices associated with the receiver, in order to tune it to the frequencies used for communication with the various shore stations authorized by the ship's radio license, or for communication with other ships, or with the U. S. Coast Guard. This crystal or tuning control may be exercised either locally by the ship's operator, or from a distant point such as a shore station or another ship. Such tuning when controlled locally may be done by keys, but when controlled from a distance is preferably effected automatically under the control of the operator at the distant station. For this purpose a step-by-step connector switch or other similar switch may be provided at the ship stations to select the proper tuning element. It is also contemplated that crystals or other devices for determining the frequency of the ship's transmitter may be selected and controlled in the same manner as those of the receiver.

For communication from ship to ship a special frequency is allocated, and all of the ships transmit and also receive on this single frequency. When one ship wishes to communicate with another, the operator at the calling ship interrupts the dialing frequency by dialing the code for the special frequency assigned for ship to ship communication, thus causing the called ship and all other ships to have their transmitters and receivers automatically tuned to the ship to ship frequency. The calling operator next actuates a key to shift his own transmitter and receiver to this frequency, and then calls the name of the desired ship by telephone. The called operator answers and conversation proceeds. Operators at other ships may restore their apparatus to the dialing frequency by operating a release key.

The provision of a special common frequency for dialing purposes means that each shore station must be able to send two frequencies-the common dialing frequency and the sending frequency assigned by the station license. A dial is provided at each shore station for sending code signals by the dialing frequency, to automatically tune the transmitter and receiver of the called ship to the receiving and transmitting frequencies of the shore station. Shifting from the dialing frequency to the sending frequency and vice versa at the shore station may be controlled by a key switch actuated by the shoe station operator.

Further details, objects and results of the invention will be clear from the following description when read in connection with the accompanying drawing, in the figure of which a preferred form of signaling system embodying the invention is disclosed.

Referring to the drawing, a typical land or shore station is shown at the left and a ship station appears at the right.

Description of land station apparatus The land station is similar to that illustrated in my Patent No. 2,265,056, above referred to, but is equipped with means to tune the transmitter to the common dialing frequency when desired and to interrupt or dial said frequency in accordance with a code. As shown the land station differs from that of my patent in that instead of 1- having a common transmitter with several different receivers associated therewith, only one receiver is associated with the transmitter. However, the present system contemplates providing each land transmitter with one or more separate receivers at nearby shore points if desired. Each shore station has an individual transmitting frequency assigned to its transmitter, and a separate frequency individual to the station is assigned to its receiver.

A shore transmitter is shown at T1 and is normally adjusted to transmit at the assigned transmitting frequency, and for this purpose a crystal CRY1 is connected to the oscillator T01 associated with the transmitter T1. When it is desired to dial a called ship station to tune its transmitter and receiver to those of the shore station, a key KD1 may be operated to disconnect crystal CRY1 and substitute crystal CRYd.

The radio receiver at the shore station is shown symbolically at R1 and has associated therewith a codan COD. The codan is a well known device and is therefore represented by a simple rectangle. It receives its name from the fact that it is a carrier operated device unresponsive to noise, the name being derived from the initials of the expression carrier operated device antinoise. The codan, in response to received carrier, operates a codan relay CR to accomplish certain results which will appear later.

For communication purposes the transmitter T1 and the receiver R1 .are connected to a jack J1 in a manner now to be described. Through this jack connections may be established by a socalled marine operator to a person on land who wishes to talk to someone aboard ship. From the jack J1 a local oifice connection Li extends to a junction point controlled by a switching relay SWR1. At this point the circuit divides into two branches. One branch TL1 extends through a vogad VG (symbolically represented) and over a path TL1 to the transmitter T1. The other branch RL1 extends over a path RL1 to receiver R1 through an assemblage of apparatus including a voice frequency amplifier, an equalizer and a pad, represented symbolically by rectangle RE. The vogad VG is a well known device for automatically adjusting gain, deriving its name from the initials of the expression voice operated gain adjusting device.

It will be noted that the relay SWR1 is located at the point where the local office connection L1 branches into the paths TL1 and RL1 leading to the transmitter T1 and R1 respectively, so that its armature determines which of said paths is connected to the local connection L1. When only the lower winding of relay SWR1 is energized, as is normally the case, its armature completes the path to the receiver R1. When the marine operator plugs into the jack J1 to establish a connection and the land station's receiving carrier is Searcn m transmitted from a ship, no current flows through the upper winding of relay SWR1 and the connection from local circuit L1 to the receiver R1 remains established. When the ship operator ticular carrier frequency being received. To this end crystals such as CYa, CYl, CYss, CYsos, etc. are arranged to be selectively connected to the oscillator ROs to determine the beating frequency.

cuts off the carrier, the upper winding of relay 5 The effective tuning of both the radio receiver SWRl is energized and said relay switches the and the radio transmitter by means of the sets local connection L1 over path 'I'Li to the transof crystals above described should be under the mitter T1 and disconnects the path to the recontrol of a shore station when the shore station ceiver R1. Thus it will be seen that switching is calling, but should also be under the control of from the transmitter to the receiver and vice the operator aboard ship to enable him to call versa at the shore station is under the control of any desired shore station, or any other ship. the talker aboard a ship communicating with Hence tuning relays such as TRd, TR1, TRss, and the shore station, because the talker switches TRsos, etc. are provided to connect individual pairs the carrier on and oil as will appear later. of crystals over their contacts I and 5 to oscil- As d scribed i my prior Patent No. lators T01; and ROs, respectively. These relays a ship operator may dial a code number repremay be selectively operated either by means of senting a desired shore station to call the operaa tep-by-step switching equipment operable from tor at such station. The dialed pulses operate the a i t t t t and including operating appacodan r l y R, wh pera s hr h relays ratus SW5, a brush Ws, and a bank of contacts IS, 1T1 and LR1 to operate a sw of D- y- 83s, or it may be operated by means of selecting step or other known types. As illustrated the keys SKl, sKss, SKsos, etc. controlled by the ship switch includes a bank of contacts 531, a wiper operator. W1 and Switch Operating and controlling app r The tuning relay 'I'Ra has its contacts so artus y a y r pres ted y t rectangle ranged that crystals CYd and CYd' are normally SW1. The equipment represented by the recconnected to the oscillators ROs and TOs, respect e includes relays similar to those desig tively, to condition the radio receiver Rs and radio 1, 1, 1", i y Drier patent above referred transmitter Ts to operate at the dialing frequency. to, as well as the off-normal switch ON, vertical When any of th ther tuning relay such a TR], st pp g net V1, rotary stepping magnet R1 TRss, etc. are operated, they actuate the relay TRd and release magnet Y1, therein shown. As these to disconnect the dialing crystals from the two elements and their mode of functioning are well oscillators At, the ame time the operated relay known. y e not illustrated or described hereat its contacts I and 5 substitutes the crystals cont e reader s referred to y Said Patent trolled thereby for the disconnected dialing crys- No. 2,265,056 for further details and the mode tal. For example, if relay TRss is operated, it Of peration. It is sumcient for our present puractuates relay TRd to disconnect the dialing crysposes to know that when the code number of the tal CYa and CYa', and over its contacts 5 and l illustrated land station is dialed, the codan relay relay TR S connects the crystals CYss and CYss' Causes th swit hin pp at 1 through its which are used for ship-to-ship communication) per W1 to close the circuit of the marine op to the oscillators ROs and TOs, respectively. ators lamp MOL t appri the operator that a 40 The switching equipment including operating Connection is deslledapparatus SWs, wiper Ws, and bank of contacts Description of ship station apparatu SBs may be in all respects similar to that already At h t t T discussed in connection with the land station and s P S anon a m ,ransml er 5 i F operates in asimilar manner. Normally the radio receiver Rs provlded' The l receiver Rs is set by means of the crystal CYc to transmitter Ts has associated therewith an oscllreceive at the dialing frequency Another Station lator TOs which determines the carrier frequency desiring to communicate with the Ship station out by F transmltter- In Order. P the illustrated will dial and thereby produce pulsatlansmlttel' may recewmg 9 tions of the dialing frequency in accordance with rler frequency of any station in communlcatlon the code designating the frequency pair of a mylmber of crysm1 such as CYd'1 quencies at which communication is to take place. CYSS CYSOS are provlded- These crystals The switch wiper Ws will be operated to make conbe selectlvely connected to the oscmator 9 nection with one of the contacts of the bank SBs a manner hereinafter change ms and thereby complete a circuit for a selected one frequency so that any deslred earner may be of the tuning relays TR1 TRss etc to switch on emitted from the transmitter Ts. The microthe proper crystals. phone or transmitter element of a handset or During communication the Switching relay type telephone set 15 conneeted to the SWRs at the ship station is used to control the rad) transmltter Ts over a transmlttmg path direction of transmission. When the ship oper- I'Ls, and may be used to modulate the carrier 00 talks he operates the relay SWRS by means sent out r h radlqtrensmltler of a key BK on the handset. The contact I of The rad) lefelver 15 connected to f said relay closes the circuit of oscillator TOs and g 3 detectmg equlpmen't for recelvmg its contact 2 opens the circuit of radio receiver dlal signals, and over a receiving pat o a Rs, so that transmission takes place from the ship loud speaker Lsfind to the fecelvelf of the hand' station transmitter to a distant station's receiver. set HS. osclllator ROs lS associated with the w the operator wishes to listen he opens the radio receiver Rs and supplies a local beating fre- Contact f key BK and relay SWRS disables the quency so related to a received modulated carrier radio transmitter and closes the circuit of the as to detect PherefrPm the telephonlc Waves in radio receiver Rs. Transmission now takes place accordance with WhlCh the carrier is modulated in the reverse direction i e f the distant at the sending station. In order that speech may station to the ship statiol'l be detected from difierent carriers transmitted I from different sending stations, the beating frecallmg from shore to ship quency supplied by the oscillator ROs must be ad- It will be understood that there may be several justable so as to be properly related to the parship stations similar to that illustrated, and that there will be a number of shore installations similar to that shown in the drawing. Any ship can call any other ship, or any shore station, and any shore station can call any ship. Let use consider first a call from a shore station to a ship. All ship station receivers in the standby condition will be tuned to the dialing frequency, because the crystals corresponding to CYa will be normally connected to oscillators such as ROS at idle ship stations.

Assuming that the shore station illustrated is calling the ship station shown in the drawing, the marine operator at the shore station inserts a plug in the jack J1 and closes key KD1 of the dialing circuit. The sleeve relay S1 is thus operated and in turn operates relay S2. In the idle condition of the circuit, before these relays are operated, the polar switching relay SWRi is actuated only by its lower or biasing winding, so that its armature rests on its contact I. In this condition it connects circuit L1 to the receiving path RL1 and maintains the transmitting path TL1 (which leads to the transmitter T1) disconnected therefrom. The receiving path RLI is normally open at contact I of relay REC, however.

Relay S2 by closing its contact I energizes relay REC, which, at its contact I closes the normally open receiving path RL1. At the same time a circuit is completed for the upper winding of polar relay SWR1 over contact 3 of relay REC as follows: From battery, through upper winding of relay SWR1, over contact 2 of relay S2, over contact I of relay LC, and over contact 3 of relay REC to ground. Relay SWRi now operates its armature to its contact 2, thus opening the connection from circuit L1 to the receiving path RL1 and establishing the connection to the transmitting path TL1.

When the marine operator ashore closes key KD1, a dialing circuit is established from ground over the contacts of said key, through dial D1, over conductor I0, over upper conductor of path TLi, and thence through the windings of relays DB1 and DRz to battery. Relay DR1 by opening contact I disconnects crystal CRY1 (which determines the normal transmitting frequency of the shore station) from oscillator T01, and at contact 2 connects crystal CRYa to said oscillator. Crystal CRYa is at the same time connected to ground over the front contact of relay DB2, and thus conditions the transmitter T1 to transmit at the dialing frequency common to all of the stations.

The crystal CYd at the ship station is normally connected to the oscillator ROS of the receiver Rs to condition it to receive at the dialing frequency. Therefore as soon as the dial frequency is received from the land station, the pulses of carrier frequency are applied to the circuit of the amplifier-detector ADS at the ship station and will cause the operation of relay ITS. Relay ITS in turn operates relay LRS to condition the switching apparatus SW5 to receive pulses.

Since the shore station will (except when dialing) transmit at a fixed frequency determined by crystal CRY1 and will receive at a different fixed frequency, the receiver and transmitter at the ship station must be conditioned to operate at these frequencies. Assuming that this may be done by selecting the crystals CY1 and CY1 at the ship station the marine operator ashore now dials a code number to select said crystals. In the case illustrated this cade number will be 05 and the hore operator now dials this number.

The first dialing operation opens the dialing Ill circuit through relays DB1 and DR: ten times. The relay DR1 is slow to release and does not fall off between pulses, but relay DR: releases its armature each time the dialing circuit is interrupted, thus interrupting the dialing frequency sent out by the transmitter T1 under control of the dialing crystal CRYd.

As all of the ship stations are normally set to receive at the dialing frequency, all idle stations will respond alike to the dialing operation- Therefore it will be understood that the description of the operation at the illustrated ship station will apply equally to the other ship stations. Each time the dialing carrier is interrupted the alternating current relay ITS is released and in turn releases relay LRS. Each time relay LRS releases the switching apparatus SW5 elevates the brush Ws a step so that at the tenth pulse the wiper is on a level with the tenth row of contacts. The shore operator now dials the digit five, which steps the wiper horizontally to the fifth contact. After the dialing operation is completed the shore operator opens dial key KD1, releasing relay DB1 and DR2, to again connect crystal CRYl to the oscillator T01, so that the transmitter is now conditioned to transmit at its normal working frequency.

When the wiper W5 comes to rest on the fifth contact of the top row of the bank SBS, a circuit is closed from battery, over said wiper and contact, and through the winding of tuning relay TR1 to ground. Relay TR1 at its contact 2 energizes relay TRd which disconnects dialing frequency crystals CYa and CYa' from the oscillators ROS and T05, respectively. Relay TR1 at its contacts 5 and I connects crystals CYl and CYi' to said oscillator, thus conditioning receiver Rs and transmitter T5 to receive and transmit at the respective transmitting and receiving frequencies assigned to the shore station illustrated. The ship station is now conditioned to communicate with the calling land station.

For the instant that is required for the relay TRa to pull up its armature after the relay TR1 operates, both crystals CYa and CY1 are connected to the oscillator ROS. This conditions the receiver R5 to receive momentarily at a frequency other than that emitted by the transmitter T1 at the land station. This would result in a momentary interruption of the carrier supplied to the relay ITS and thus might cause the relay LRS to release the switch SW5. To prevent this, relay TR1 connects ground over its contact 4 to briefly lock up the circuit of relay LRs during the time required by slow operating relay SOR to open said locking circuit. At its contact 3 relay TR1 closes a circuit for the lamp LP1 to apprize the ships operator that a call has come men the ship-shore channel. Similar lamps are lighted at all other idle ship stations.

Upon seeing the lamps light each ship operator removes his handset HS from the switch-hook SH and, if he wants to talk, momentarily operates selecting key SK1. Key SK1 operates selecting relay SR1 which in turn locks up tuning relay TR1 from battery, over switch-hook SH, and over lower contact of relay SR1. Relay SR1 closes its upper contact to lock up relay LRs 0f the switch SW5 so long as the receiver is off the switchhook. This prevents any possibility of the switch SW5 being restored to normal and the receiver returned to the dialing frequency each time the ship's transmitter is turned on. If it were not for this feature, each time the transmitter TS is conditioned to transmit the cons HM current disabling of receiver R11 by relay SWR; it would cut off the received carrier, thus releasing relay ITS and the switch SW5. All of the ship sets are now conditioned to communicate with the calling land station and the ship operators use their handsets to listen for the land operator to call the name of the ship with which communication is desired.

The land station operator, after restoring the dialing circuit, talks over the connection L1. As no ship is sending out the land stations carrier, the upper winding of relay SWR1 is energized and the armature of said relay is on contact 2, thereby connecting circuit L1 over transmitting path TL1 to the transmitter T1. The land operator, talking over this path, calls out the name of the wanted ship station in the usual manner. The operators at unwanted ship stations, upon hearing this, hang up their handsets, thereby releasing selecting relay SR1 and unlocking tuning relay TR1 and relay LRS at such ships. Said operators then momentarily open their keys RK to release the relays corresponding to ITS long enough to cause the switches SW5 at unwanted stations to be released and restored to normal. This releases tuning relays corresponding to TR1 at unwanted ships, and again conditions their sets for transmission and reception at the dialing frequency. If any ship stations are unattended they will be restored to dialing frequency when the shore station goes oil the air, as this interrupts the carrier received at such ship stations and releases their relays corresponding to ITS and LRs.

The operator at the called ship station can talk to the shore station by operating the button key BK on the handset HS. This energizes relay SWRS to disable receiver RS and close the circuit of oscillator T05, so that transmitter Ts can send out its carrier. Said carrier when received by receiver R1 at the shore station causes the codan relay CR to clos a circuit from the grounded contact of relay CR, through the winding of relay IS, over lower conductor of path RLi', and through upper winding of polar relay LC to battery. Relay LC opens contact I thereby de-energizing the upper winding of relay SWR1. Relay SWRi shifts its armature from its contact 2 to contact I, thus connecting circuit L1 to the receiver R1 s long as the carrier is sent out from the ship station.

The ship station operator replies to the shore operator and then releases the button BK. This cuts off the transmitting carrier, whereupon relay SWR1 at the shore station shifts the connection from circuit L1 back to the transmitter T1. The shore operator is now able to talk again to the ship operator. Thus it becomes evident that the shore station is shifted between talking and receiving condition by the ship operator manipulating the key BK associated with the handset HS. At the end of the conversation the ship operator, by hanging up his handset HS and momentarily opening release key RK, restores his set to normal as already described in connection with unwanted stations, and conditions the ship set to transmit and receive at dialing frequency by the release of tuning relay TRd.

While only one relay TR1 and its associated shore station crystals CY1 and CY1 have been shown, it will be evident that other selecting relays similar to TR1, each having associated crystals. will be provided to tune the ship receiver and transmitter for communication with other shore stations. If another shore station wishes to call, the operator thereat will dial the number designating its assigned carrier frequencies. There- Searcn 00" upon the switch SW. at the ship station will be operated to establish a circuit for the proper relay similar to TR1 at such station, and the ship station will be conditioned by the selection of proper crystals to communicate with the calling land station.

Calling from ship to shore If the ship operator at the illustrated ship station desires to call a land station, he removes the handset HS from the switch-hook SH, and then momentarily depresses a selecting key such as SK1 which corresponds to the desired land station. Only the key SK for calling the illustrated shore station is shown, but it will be understood that other keys will be provided to select other shore stations. Assuming the land station illustrated is to be called, selecting key SKI is operated. This energizes selecting relay SR1 which in turn completes a circuit from battery, over the switch-hook SH, and through the winding of tuning relay TR1 to ground. Relay TR1 operates relay TRd, thus disconnecting crystals CYd and CYd' and substituting crystals CY1 and CY1, so that receiver R5 and transmitter Ts are respectively tuned to the transmitting and receiving carrier frequencies of the shore station. The shore station, it will be understood, has its transmitter T1 and receiver R1 normally tuned to these frequencies.

The ship operator now presses the button switch BK on his handset HS to actuate relay SWRs, thus disabling receiver R, and conditioning transmitter Ts to send out the carrier frequency determined by crystal CY1. Having done this the operator manipulates the dial D! to dial the code call for the desired land station, thus interrupting the ship's carrier in accordance with the pulses of the code. Let us assume that the call number assigned to the land station illustrated is 50. Before dialing starts, relay SWR11, under the control of the ship operator. causes the ship transmitter to send out the carrier at which the land station normally receives, thus operating codan relay CR.

Codan relay CR closes the circuit previously described for relays IS and LC. The operation of the latter relay is without effect, as both circuits controlled by its armature are open at other points. Relay IS, however, actuates relay IT1 which in turn operates relay LR1 to prepare the switching apparatus SW1 for the stepping operation. When digit 5 is dialed the relay LR1 is interrupted 5 times and the wiper W1 is stepped to the level of the fifth row of contacts in the bank SB1. Upon dialing the digit 0 the wiper is moved horizontally ten steps and comes to rest on the last contact in the fifth row.

The switch now completes a circuit from battery, through relay LL, over wiper W1 and the last contact of the fifth row, over back contact 2 of the sleeve relay S1, and through lamp MOL to ground. Relay LL locks the lamp circuit independently of the wiper W1 and the lamp n0- tifies the operator that a call has come in. The ship operator at the end of the dialing operation releases key BK, thus disabling the transmitter T5 and again conditioning the receiver R5 'to receive at the transmitting frequency of the shore station. Disabling the transmitter Ts cuts off the carrier, releasing the codan relay CR and the chain of relays IS, IT1 and LR1 to restore the switch SW1 to normal.

The marine operator at the land station, observing the signal, plugs into the jack J1 and operates sleeve relay Si which at its contact 2 opens the lamp circuit and, releases locking relay LL. At its contact I relay S1 operates relay S2 which in turn operates relay REC. Relay REC at its contact I closes the receiving path RL1 and at its contact 2 closes the circuit previously traced through the upper winding of switching relay SWR1. Relay SWRl operates its contact 2 to disable the receiving path RLI and closes its contact 2 to connect circuit Ll over the transmitting path TLi to the transmitter T1. The operator now talks to the ship operator over the carrier determined by the crystal CRY] associated with transmitter T1 and conversation proceeds. The ship operator can now manipulate the button key BK of his handset, thus shifting at both stations from east bound carrier to west bound carrier, and vice versa. in the manner already described.

At the end of the call the shore operator removes the plug from jack J1 to restore the land station apparatus to normal. The ship operator returns the handset to switchhook SH, thereby unlocking selecting relay SR1. This releases tuning relay 'I'Ri which in turn releases relay TRd. The transmitter Ts and receiver Rs are thus again conditioned to operate at the common dialin frequency.

Calling from ship to ship All ship-to-ship calls are made on a single common carrier frequency which is assigned for that purpose and is used for both transmitting and receiving. This enables any ship to talk to all other ships simultaneously if desired. When the call is only for a particular ship, the calling ship operator so signifies by calling the name of the ship, and the operators at other ships can then hang up their receivers and let the conversation proceed exclusively between the two ships concerned.

Assume that a ship-to-ship frequency requires that at each ship a crystal CYss' to be connected to the oscillator of the transmitter Ts and a similar crystal CYss to be connected to the oscillator of the receiver Rs. The calling ship operator removes the handset HS from the switch-hook SH and operates the button key BK to turn on the transmitter Ts and disable receiver Rs. The transmitter is set to operate on the dialing frequency determined by crystal CYd' as relay IR; is not operated. The operator now dials the code number assigned for ship-to-ship transmission, which we will assume to be 06.

Upon dialing the digit the dialing frequency sent out by the transmitter Ta is interrupted ten times. This is followed by dialing the digit 6 which produces six such interruptions. Having dialed the code number to operate switches similar to SWs at all other ship stations in a manner about to be described, the ship operator momentarily operates selecting key SKss. This operates selecting relay SRss and locks it up over the switch-hook SH. Relay SRss operates tuning relay TRss to connect crystals CYss and CYss' to the receiver Rs and transmitter Ts respectively. Relay TRss at its contact 2 operates relay TRd to disconnect the dialing crystals CYa and CYa'. The transmitter and receiver at the calling station are now tuned to transmit and receive at the ship-to-ship frequency. Holding his button key BK operated the calling operator calls out the name of the desired ship by voice in the usual manner. Each time he talks the operators local receiver is disabled by the action of the button key BK and the switching relay SWRs, thus preventing side tone in the ear of the operator.

At all other ship stations the interruption of the dialing frequency by dialing the ship-to-ship code number 06 causes identical operations. The relays corresponding to ITs are released for each interruption and the wiper Ws is moved to the sixth contact of the tenth level to complete an obvious circuit for the tuning relay 'I'Rss. This relay at its contacts I and 5 connect crystals CYss' and CYss to the transmitter Ts and receiver Rs respectively. At its contact 2 it operates relay TRd to disconnect crystals CYa' and CYd. At its contact 3 it lights a lamp LPss and at its contact 4 it momentarily locks up relay LRs to prevent possible release of the switch during the interval both crystals CYd and CYss are connected to the oscillator ROs associated with the receiver Rs.

The transmitters and receivers at all ships are now tuned to the ship-to-ship frequency and are in condition to send and receive voice calls. The lighting of the lamps corresponding to LPss at all ships apprize all ship operators that a call is waiting on the ship-to-ship channel. Each operator now removes his handset HS from the switchhook and listens to hear the name of the ship being called. All operators other than the called operator, upon hearing the name of the called ship, hang up their handsets to restore the locked up relays and momentarily release their keys corresponding to key RK to release the step-bystep switches. All uncalled ship stations are now normal.

The operator at the called ship station, upon hearing the name of his ship announced, momentarily depresses key SIQs and locks up relay SRss over the switch-hook SH. Relay sRss at its lower contact locks up relay TRss selected by the switch SWs, and at its upper contact locks up relay LRs to prevent the receiver corresponding to Rs being returned to dialing frequency when the called ship's transmitter is turned on and the receiver disabled so that the carrier operated relay ITs is released. Both the calling and called ships have their transmitters and receivers tuned to the ship-to-ship frequency, and conversation may proceed. Each talker operates the button key BK while talking, thus disabling the local receiver and preventing side-talk. At the end of the conversation the operators hang up and momentarily open their keys RK, thus restoring all apparatus to normal.

Distress calls Distress calls are made in the same manner as other ship-to-ship calls. The calling ship operator dials a special SOS code call which we will assume is 07. At all other ship stations the interruption of the dialing frequency in accordance with the code call steps the switches corresponding to SWs to the seventh contact of the tenth row at each station. This operates the selecting relay TRsos at each station, thus ringing the SOS gongs Gsos on each ship over contact 3 of the selected relay.

Each operator, upon hearing the gong, removes his handset from the switch-hook. If he desires to take part in the conversation, he may, by operating his key corresponding to SKsss, lock up the selected relay TRaos with results similar to those described in connection with ordinary ship-toship calls. The calling operator will, of course, after dialing, operate his key sKsos to operate and lock up relay TRsos and shift the tuning of his transmitter and receiver from the dialing frequency to the ship-to-ship frequency. All opernivva lllbvlllq I ators who have not hung up now have their receivers and transmitters tuned to the ship-toship frequency, and conversation may proceed in the usual manner.

Calling from a ship to Coast Guard stations A call from a ship to the Coast Guard is made in substantially the same manner as a ship-toship call. For a Coast Guard call a common frequency is used by all stations, just as in ship-tship transmission, except that the frequency is different from that used for communication between ships. For calling the Coast Guard another key similar to SKss is used to operate a selecting relay similar to SR and a tuning relay similar to TRss. Said key and relays are not shown as their connection and functioning is obvious from what is illustrated and described with respect to ship-to-ship communication.

Other uses It will be obvious from the foregoing that the system herein described may be used for communication between airplanes and ground stations, and for use in communicating between planes.

Similarly the system might be used for communication between vehicles of all kinds, such as trains, automobiles, trucks, etc., and between such vehicles and fixed stations.

While this invention has been disclosed in certain specific arrangements which are deemed desirable, it will be obvious that the general principles herein set forth may be embodied in many other organizations, widely different from those illustrated, without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for twoway communication over the assigned channel only, a; plurality of mobile stations each arranged for two-way communication over any of a plurality of two-way channels having different frequencies and having frequency determining means thereat, and means at each fixed station to automatically adjust the frequency determining means at a municate over the channel assigned to said fixed station.

2. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for twoway communication over the assigned channel only, a plurality of mobile stations each arranged for two-way communication over any of a plurality of two-way channels having different frequencies and having frequency determining means thereat, switching means at each mobile station to selectivel adjust said frequency determining means, and means at each fixed station to selectively control the switching means at a mobile station to selectively adjust the frequency determining means thereat to enable it to communicate over the channel assigned to said fixed station.

3. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for twoway communication over the assigned channel only, a plurality of mobile stations each arranged for two-way communication over any of a plumobile station to enable it to com- OUdlhll huum rality of two-way channels having different frequencies and having frequency determining means thereat, a dialing frequency common to all of the stations, means at each fixed station to dial said dialing frequency in accordance with a code, and means at each mobile station responsive to dialed codes to adjust the frequency determining means at said station to enable it to communicate over the channel assigned to a particular fixed station.

4. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for twoway communication over the assigned channel only, a plurality of mobile stations each arranged for two-way communication over any of a pinrality of two-way channels having different frequencies and having frequency determining means thereat, a dialing frequency common to all of the stations, means at each fixed station to dial said dialing frequency in accordance with a code, and switching means at each mobile station operating in response to a code sent out from a fixed station to selectively adjust said frequency determining means at said station to enable it to communicate over the channel assigned to said particular fixed station.

5. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for two-way communication over the assigned channel only, a plurality of mobile stations each arranged for two-way communication over any of a plurality of two-way channels having different frequencies and having frequency determining means thereat, a dialing frequency common to all of the stations, means at each fixed station to dial said dialing frequency in accordance with a code, switching means at each mobile station operating in response to a code sent out from a fixed station to selectively adjust said frequency determining means at said station to enable it to communicate over the channel assigned to a particular fixed station, and means at each mobile station whereby the operator thereat, upon learning that the call is intended for another station, may restore the mobile station to the common dialing frequency.

6.In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto and having its transmitter normally adjusted to transmit at the transmitting frequency of the channel, each fixed station being arranged for two-way communication over the assigned channel only, a plurality of mobile stations each arranged for two-way communication over any of a plurality of two-way channels having different frequencies and having frequency determining means thereat, a dialing frequency common to all of the stations, means at each fixed station to adjust its transmitter to the common dialing frequency means at each fixed station to dial said dialing frequency in accordance with a code, and means at each mobile station responsive to dialed codes to adjust the frequency determining means at said station to enable it to communicate over the channel assigned to a particular fixed station.

7. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto and having its transmitter normally adjusted to transmit at the transmitting frequency of the channel, each fixed station being arranged for two-way communication over the assigned channel only, a plurality of mobile stations arranged for two-way communication over any of a plurality of two-way channels having difierent frequencies and each having frequency determining means thereat, a dialing frequency common to all of the stations, means at each fixed station to adjust its transmitter to the common dialing frequency, means at each fixed station to dial said dialing frequency in accordance with a code, and switching means at each mobile station operating in response to a code sent out from a fixed station to selectively adjust said frequency determining means at said station to enable it to communicate over the channel assigned to a particular fixed station.

8. In a signaling system, a plurality of fixed stations each having a different fixed frequency twoway communication channel assigned thereto and having its transmitter normally adjusted to transmit at the transmitting frequency of the channel, each fixed station being arranged for two-way communication over the assigned channel only, a plurality of mobile stations arranged for twoway communication over any of a plurality of twoway channels having different frequencies and each having frequency determining means thereat, a dialing frequency common to all of the stations, means at each fixed station to adjust its transmitter to the common dialing frequency, means at each fixed station to dial said dialing frequency in accordance with a code, switching means at each mobile station operating in response to a code sent out from a fixed station to selectively adjust said frequency determining means at said station to enable it to communicate over the channel assigned to a particular fixed station, and means at each mobile station whereby the operator thereat, upon learning that the call is intended for another station, may restore the mobile station to the common dialing frequency.

9. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for two-way communication over the assigned channel only, a plurality of mobile stations each arranged for two-way communication over any of a plurality of two-way channels having different frequencies and having a plurality of frequency determining elements thereat, one for each fixed station twoway high frequency communication channel, and means at each mobile station for selecting, under the control of the mobile station operator, the frequency determining element thereat corresponding to the channel assigned to a fixed station with which it is desired to communicate.

10. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-Way communication channel assigned thereto, each fixed station being arranged for two-way communication over the assigned channel only, a plurality of mobile stations arranged for twoway communication over any of a plurality of two-way channels having different frequencies and having a common two-way high frequency communication channel for intercommunication between mobile stations, each mobile station having a plurality of frequency determining elements thereat, one for each fixed station two-way high frequency communication channel and one for said common two-way high frequency channel, and means at each mobile station for selecting,

under the control of the mobile station operator, the frequency determining element thereat corresponding to a fixed station channel when it is desired to communicate with a fixed station, or the frequency determining element corresponding to said common high frequency channel when it is desired to communicate with another mobile station.

11. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for twoway communication over the assigned channel only, a plurality of mobile stations arranged for two-way communication over any of a plurality of two-way channels having different frequencies and having a common two-way high frequency communication channel for intercommunication between mobile stations, each mobile station having frequency determining means thereat whereby it may communicate with any desired fixed station over the assigned high frequency channel thereof or with another mobile station over said common two-way high frequency channel, and means at each mobile station to automatically adjust the frequency determining means at another mobile station to enable it to communicate over said common two-way channel.

12. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for two-way communication over the assigned channel only, a plurality of mobile stations arranged for twoway communication over any of a plurality of twoway channels having different frequencies and having a common two-way high frequency communication channel for intercommunication between mobile stations, each mobile station having frequency determining means thereat whereby it may communicate with any desired fixed station over the assigned high frequency channel thereof or with another mobile station over said common two-way high frequency channel, code operated means at each fixed station to operate a signal thereat in response to a code individual to that station, code operated means at each mobile station responsive to a particular code to adjust the frequency determining means thereat to said common two-way high frequency communication channel, and means at each mobile station to send codes to selectively operate signals at said fixed station or to adjust the frequency determining means at another mobile station to said common two-way high frequency communication channel.

13. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for twoway communication over the assigned channel only, a plurality of mobile stations arranged for two-way communication over any of a plurality of two-way channels having different frequencies and having a common two-way high frequency communication channel assigned thereto for intercommunication between mobile stations, each mobile station having frequency determining means thereat whereby it may communicate with any desired fixed station over the assigned high frequency channel thereof or with another mobile station over said common two-way high frequency communication channel, a dialing frequency common to all of the stations, code operated means at each fixed station to operate a signal thereat in response to a code individual to uuul Ull nuu|| that station, code operated means at each mobile station responsive to a particular code to adjust the frequency determining means thereat to said common two-way high frequency communication channel, and means at each mobile station to dial codes to selectively operate signals at said fixed stations, said last mentioned means also operating to modify said dialing frequency in accordance with a code to adjust the frequency determining means at another mobile station to said common two-way high frequency communication channel.

14. In a signaling system, a plurality of fixed stations each having a different fixed frequency two-way communication channel assigned thereto, each fixed station being arranged for twoway communication over the assigned channel only, a plurality of mobile stations arranged for two-way communication over any of a plurality of two-way channels having different frequencies and having a common two-way high frequency communication channel assigned thereto for intercommunication between mobile stations, each mobile station having frequency determining frequency channel thereof or with another mobilestation at said common two-way high frequency communication channel, a dialing frequency common to all of the stations, code operated means at each fixed station to operate a signal thereat in response to a code individual to that station, code operated means at each mobile station responsive to a particular code to adjust the frequency determining means thereat to said common two-way high frequency communication channel, means at each mobile station to dial codes to selectively operate signals at said fixed stations, said last mentioned means also operating to modify said dialing frequency in accordance with a frequency determining code, and means at each mobile station responsive to said dialing frequency when modified by a particular code at another mobile station to adjust the frequency determining means at said first mentioned fixed station to said common two-way high frequency communication channel.

ALBERT FRANKLIN BOWERS.

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