US2290079A - Multiplex channel repeater system - Google Patents

Description

July 14,1942. 6. s. VERNAM MULTIPLE)! CHANNEL REPEAI-ER SYSTEM Filed Dec. 20, 1940 4 Sheets-Sheet l INVENTOR. albez'l -51 l ernam ATTORNEYS 19o BY y 1942- G. s. VERNAM 2290.079

MULTIPLEX CHANNEL REPEATER SYSTEM Filed Dec. 20, 1940 4 Sheets-Sheet 2 W L- To ASSOCIATED p l :1 W B REPEATER 6 L Lfl hhjlz I17 M T Li I Wun l v r94- l i V 5 INVENTOR. Gilbert 5'. Verna/11 BY 8% r A TTORNE Y$ July 14, 1942. cs. 5. VERNAM MULTIPLEX CHANNEL BEPEATER SYSTEM Filed Dec. 20. 1940 4 Sheets-Sheet 3 ZOrCflOl Kin-Z IO INVENTOR; Gilbert 5. Her/Lam BY $9M?!" A TTORNEYs y 1942- cs. s. VERNAM 2,290,079

MULTIPLEX CHANNEL REPEATER SYSTEM Filed Dec. 20, 1940 ,4 Sheets-Sheet 4 A T TORNE YS Patented July 14, 1942 TS PTNT FFICE MULTIPLE-X CHANNEL REPEATER SYSTEM Application December 20, 1940, Serial No. 370,933 16 Claims. (01. 17852)- The present invention relates to multiplex telegraph systems, and particularly to a repeater for connecting a channel of one multiplex telegraph circuit with a channel of another such circuit, irrespective of the synchronous speed of the two circuits. Ordinarily the repeater of this invention will be utilized to receive signals from a channel of a multiplex terminal set and to repeat those signals to a channel of another multiplex terminal set. The two sets may be operating at the same or different speeds.

In prior systems of this general type the repeater included means for receiving signals from a multiplex circuit, means for temporarily storing those signals, and means for taking the signals from the storage means and applying them to the proper channel segments of the sending distributor of the second multiplex circuit. If the two circuits were operating at different speeds, as is customary, it was necessary to stop the rotary switch which served as the means for transferring the signals from the storage means to the sending distributor, and thereby to permit the rotary switch which served as the means for transferring the signals from the receiving distributor to the storage means to catch up. In the present invention it is unnecessary to stop the rotary switch on the sending side of the repeater, but instead means are provided for causing the rotary switch on the receiving side of the repeater to take two steps at certain times whereby it is prevented from lagging behind the sending switch.

In systems of this type it is necessary that the eiiective signal speed on the receiving side of the repeater be no greater than the speed on the sending side of the repeater. In order to assure this, means are provided to cause the transmitter at the distant end of the line and connected to the receiving side of the repeater to periodically send a blank or idle signal thereby reducing the effective signal speed on the receiving side to or below the speed of the sending side.

In a prior system for achieving this the means for reducing the effective transmitter speed included an electron discharge tube having a storage condenser in its grid circuit. This means, though operable, is relatively complicated and difficult to maintain. In the present invention a simple means for bringing about this same result is provided, this means comprising a rotary switch which is inserted in the transmitter actuating circuit and which is eilective to periodically prevent operation of the transmitter during a single cycle of the associated transmitting distributor to thereby cause an idle signal to be sent over the line to the receiving side of the channel repeater.

The present invention further contemplates an alarm circuit which will operate whenever the transmitter at the distant end of one line section is operating at a rate of speed which differs from the speed of operation of the second line section, to an extent greater than the signal storage capacity of the multiplex channel repeater.

In addition to the equipment briefly mentioned above, my present invention includes a circuit for monitoring the repeater. This circuit is so arranged that a monitoring printer may be inserted in the repeater circuit in such manner as to receive the signals directly from the multiplex receiving distributor or to receive the signals from the sending side of the repeater to determine whether the signals passing to the outgoing line are satisfactory. In addition the circuit is so arranged that signals may be originated from a transmitter included in the monitoring equipment, passed through the repeater, and received on a monitoring printer, thereby to determine whether or not the repeater is operating properly. Furthermore, this monitoring equipment may be utilized as a temporary communication circuit by connecting the monitor transmitter to one of the line sections through the repeater and by connecting the monitoring printer to the same line section on the receiving side of the channel repeater operating to pass signals in the opposite direction.

It will be obvious that the channel repeater of this invention may be utilized also in connection with multiplex start-stop translator equipment, as for example such equipment as is disclosed in the Hallden Patent No. 2,196,069 of April 2, 1940.

It is an object of my invention to provide a multiplex channel repeater in which the proper relationship of the rotary switches or like means on the receiving and sending sides of the repeater is maintained through the use of a circuit which causes the rotary switches on the receiving side of the repeater to take a double step at intervals determined by the relative positions of the switches on the sending and receiving side.

It is another object of my invention to provide an alarm circuit which will operate whenever the speed difference between the received signals and the sending equipment exceeds the storage capacity of the repeater.

It is a further object of my invention to provide a simple and effective means for reducing the effective sending rate of a transmitter by periodically stopping the transmitter and causing it to send an idle or blank signal.

It is a still further object of my invention to provide a monitoring means whereby the operation of a multiplex channel repeater may be checked.

Other objects and features of the invention will appear when the annexed specification is n considered in connection with the appended drawings, in which Figures 1 and 2, taken together, form a circuit diagram of a multiplex channel repeater.

Figure 3 is a circuit diagram of a transmitter control mechanism adapted to reduce the effective speed of a multiplex transmitter.

Figure 4 is a chart showing the frequency with which the circuit of Figure 3 causes the multiplex transmitter to send blank or idle signals for each setting of the control switch of Figure 3.

Figure 5 is a schematic diagram of a circuit for monitoring the input and output of the repeater of Figures 1 and 2.

From the foregoing it will be apparent that the multiplex channel repeater of this invention receives from a receiving multiplex distributor the five signal impulses constituting one character in the five unit code and stores those impulses for a fraction of a second, and at the proper instant releases those impulses to a sending multiplex distributor. The signals sent out from the repeater usually lag two or three characters behind the signals received by the repeater,

and therefore the repeater is designed to store a maximum of five characters.

Signals from the multiplex printer relay, through the multiplex receiving distributor, op-

erate the receiving-selecting relays is through (Fig. 1). These relays correspond to the selecting magnets of a multiplex printer and operate in a similar manner. The signals are then transferred from these relays through a stepby-step rotary switch to a group of five condensers, this group comprising one condenser from each of the groups 42 through 45.

There are five groups of condensers 42 through 46, as mentioned above, which are switched into the circuit successively so that five complete character signals can be stored before the condensers must be re-used. The stored signals are transferred successively from the condensers through a second step-by-step rotary switch 58 to the five sending selecting relays 16 through 88 (Fig. 2). The contacts of these relays correspond to the contacts of a multiplex tape transmitter and control the transmission of the signals through the sending distributor to the second line section.

The receiving rotary switch 30 steps its wipers one step for each revolution of the receiving distributor and in like fashion the sending rotary switch 50 steps its Wipers one step for each revolution of the sending distributor. Since the distributors run at difierent speeds, it would be obvious that the switches would step at different rates. For proper operation of the repeater, however, the sending switch 50 must always lag at least one step behind the receiving switch 30, and as there are but five sets of storing condensers 42 through 46, it is obvious that the sending switch must not be allowed to lag as much as five steps behind the receiving switch.

If the repeater is operating from slow to fast, that is, repeating signals from the slower receiving distributor to a faster sending distributor, the sending rotary switch 50 will tend to gain on the receiving rotary swtich 3B. To prevent the sending switch from catching up to and passing the receiving switch, the circuits are so arranged that whenever the wipers of the sending switch are but one step behind those of the receiving switch, the receiving switch is, on its next operation, caused to take two steps. This double stepping action is controlled by a control relay which will later be described.

When such double stepping occurs, one set of storing condensers is passed over without being charged, thereby causing the sending relays to transmit an idle signal. As a result of this action the repeater automatically introduces sufficient idle signals or blanks in the train of outgoing signals to compensate for the difference in speeds of the two distributors, the receiving rotary switch always taking exactly the same total number of steps as the sending rotary switch despite a speed difference between the receiving and sending distributors.

When character signals from the remote transmitting station stop, idle signals, that is, signals having no selecting impulse, are received at the repeater thus causing the receiving rotary switch 30 to stop. Under these circumstances the sending switch continues to step until all signals stored in the condensers have been transmitted and then it too stops, being at this time one step behind the receiving switch.

If the repeater is operating from fast to slow, or in other. words if the receiving distributor is running faster than the sending distributor, the receiving switch 30 will, of course, tend to gain on the sending switch 50 but due to the fact that idle signals are received at regular intervals from the remote transmitting station due to the use at that station of the transmitter control unit shown in Figure 3, and subsequently to be described, the receiving switch wipers will stop periodically in order to allow the sending switch wipers to catch up. While the wipers are stopped the condensers are not charged, and thus the next character signal is received and stored on the group of condensers immediately following that on which the preceding character signal is stored, thereby dropping out the idle signals and compensating for the speed difference.

Since it is not possible with the transmitter control circuit of Figure 3 to match the effective signal speed of the signals on the first line section exactly to the signal speed of the sending distributor from the second line section, the transmitter control circuit will stop the transmitter slightly more often than is necessary. As a result of this the sending switch 50 will occasionally approach within one step of the receiving switch 3!] and cause the receiving switch to double step. This will always occur immediately after the receiving switch has stopped as this is the only time that the sending switch can catch up to it. Occasionally idle signals will therefore be transmitted from the repeater but they will be fewer than the number received.

For example, if we assume that the first line section is operating at 60 words per minute, and

a channel thereof is connected through the channel repeater to a channel of a second line section operating at 52 words per minute, then the transmitter control circuit at the distant end of the first line section would be set to stop the transmitter after every fifth character thus reducing the effective character signal speed to five-sixths of 60 or 50 words per minute. Most of the idle signals transmitted from the sending station will be dropped out at the repeater as explained above, but on will be transmitted after every 25 characters to increase the speed from 50 to 52 words per minute.

If the repeater is receiving signals from a channel operating at a higher speed than the channel into which the repeater is sending, and if the average received signal speed is not sufficiently reduced by the transmitter control circuit, signals will accumulate at the repeater and errors will result, since under these conditions the receiving rotary switch will gain continuously and its wipers will pass the terminals that are connected at the moment to the sending switch wipers. In order to warn of this condition an off speed alarm has been provided which is controlled by a relay and which will be described subsequently.

As has been indicated above, two repeaters are always required, one for repeating signals in one direction and one for repeating signals in the opposite direction. These two repeaters are so interconnected that when the transmitter locking switch on one multiplex set is operated, the sending relays of the repeater which is sending into that set will be released to send idle signals, while the other repeater will send letter signals back over the other line to serve as a stop signal. The reception of letter signals notifies the operator not to send on this channel as it is out of service beyond the repeater. During times when the multiplex cir cuits are being synchronized and phased preparatory to being put into service, idle signals will be sent out by both repeaters, certain control relays being provided for this purpose as will later appear.

Operating circuit-receiving selecting relays Relays [6 through 20 inclusive are connected to the receiving segments II through i respec-- tively of the particular channel of the receiving distributor, and are operated in accordance with the code signals received by the printer relay it] as the distributor brush passes over the segments associated with the channel. Each of the relays it through 28 has a primary or operating winding and a secondary or locking winding. t is only necessary for a short impulse from the distributor segment to close contacts A of one of these relays and then current flowing from battery through the locking winding of that relay to ground at contacts C of control relay 23 to completely operate the relay and close the remaining contacts thereof. It will be obvious that the receiving selecting relays I5 through 29 operate in accordance with the code combination received. For example, when the letter a. is received, relays I6 and I! will operate and locx, while when the letter Z) is received, relays l6, l9 and 20 will operate and lock, and so on in accordance with the well known five unit printer code.

After the selecting impulses have been received, and selected ones of the relays it through 20 operated as described above, the sixth pulse contacts 24 will close at a time determined by the sixth pulse cam 22. Closure of the sixth pulse contacts 28 will complete a circuit leading through contacts B of receiving selecting relays l6 through 29, and through the Ope Winding of control relay 25 to ground. Due to the fact that the circuit for control relay 25 extends through contacts B of all five selecting relays in parallel, it will be obvious that at least one of these selecting relays must have operated before relay 25 can operate. It is thus apparent that when idle signals are received relay 25 does not operate and the receiving side of the repeater remains inoperative.

The secondary winding of relay 25 is shortcircuited at its contacts D when the relay is operated. When at the termination of the sixth pulse the circuit to the primary winding of relay 25 is opened at the sixth pulse contacts 24 a current is induced in the secondary winding which holds the relay operated for a fraction of a second. This, in eiTect, increases the length of the sixth pulse and insures proper operation of the stepping magnet 28 of rotary switch 30 even when distributors having a short sixth pulse are used.

Relay 25 operates relay 23 which, in turn, releases the receiving selecting relays l6 through 20 by opening their locking circuits at contact C. Relays 25 and 23 must, however, both release before the distributor brush completes its revolution so that relay It will be properly locked if it should be operated by the next character signal.

Charging the storing condensers While operating selecting relays remain operated, the sixth pulse relay 25 operates and applies battery through its contacts E and through contacts C of the operated selecting relays and wipers of rotary switch at, to charge a group of five condensers comprising one condenser from each of the groups 42 through 6. This charging action takes place very soon after relay- 25 operates, and the condensers are completely charged before the selecting relays it through 20 release.

Stepping the receiving rotary switch Sixth pulse control relay 25 operates the stepping magnet 28 of the rotary switch 30. When the magnet 23 operates, its contacts C remove a short-circuit from a resistance 3|, and thus include that resistance in the circuit of the magnet winding. This arrangement provides a strong current for operating the magnet 28 quickly, but reduces the current by causing it to flow through resistances 21 to 3| in series when the magnet has operated, thereby saving current and preventing overheating of the magnet in case the receiving distributor should be stopped and left with the sixth pulse contacts 24 closed.

Magnet 28 advances the ordinary pawl and ratchet mechanism of stepping switch 30 to its next tooth, and when relay 25 releases magnet 28 also releases and steps the wipers of the switch ahead one step, thereby connecting the relays I6 through 20, respectively, to another group of five condensers comprising one condenser from each of the groups 42 through 46, leaving the first character signal stored on the first set of condensers.

The same operations as described above are repeated for each revolution of the receiving distributor until five successive character signals have been stored in the condensers 42 through 46. The sixth received character is stored on the same condensers as the first received character but, of course, these condensers will have in the meantime been discharged through the sending relays. These operations continue as long as message signals are received.

Stepping the sending rotary switch and operating the sending-selecting relays As has been indicated above, there are provided five sending-selecting relays 16 through 80, each of these relays having an armature which is connected to a corresponding one of the segments 9| through 95 of a sending multiplex distributor, the cooperating contacts C and D of these relays being connected to battery (see Fig. 2), the contacts of the fifth pulse relay 80 being reversed in the same manner as is customary in connection with the fifth contacts of the multiplex tape transmitter, and for the purpose of transmitting signal reversals when the distributor is running idle. The operating windings of relays 16 through Bil are connected through the wipers of the sending rotary switch 50 to the same condensers as store the received impulses. The sending sixth pulse control relay 8|, by closing its contacts B, operates the stepping magnet 88 of the sending rotary switch 50. Thus relay 8|, by opening its contacts A also releases any of the sending-selecting relays 16 through 80 which has been previously operated. When relay 8| releases, the magnet 88 also releases, and steps the switch wipers of switch 50 ahead to thereby connect the sending-selecting relays to the next group of condensers. Those condensers of the group which were previously charged under control of the receiving-selecting relays now discharge through corresponding ones of relays 16 through 80 operating those relays which correspond to selecting impulses in the stored signal. Operated ones of these relays lock in their operated position due to completion of the circuit through contacts A of these relays and contacts A of relay 8|.

The character signal set of relays 1% through 89 is sending multiplex distributor, after which relay 8| again operates due to completion of the sixth pulse circuit through sixth pulse contacts 82 of the winding of relay 81. Thus operation of relay 8! serves, as described above, to release the selecting relays and to cause the rotary switch to step, select and discharge the next group of condensers into the selecting relays. These operations continue as long as there are any stored signals to transmitted.

up on the contacts Double stepping circuit The foregoing has explained how character signals are received from one channel of the receiving multiplex distributor on the receiving relays !6 through 28, transferred through receiving rotary switch 39, to condensers of the five groups 42 through it, and then again transferred from the condensers through the sending rotary switch 59 to sending relays '56 through 8G from which the signals are sent out through a channel of a sending multiplex distributor to the second line section. From this description it is obvious that even though the two distributors may run at different speeds the sending rotary switch must always be not less than one, nor more than four steps behind the receiving switch. As indicated, in order to maintain this relation when the repeater is repeating from a faster to a slower channel, the receiving switch is stopped periodically by transmitting idle signals from the sending station. This stopping action drops out the transmitted by the idle signals and tends to make the receiving switch take fewer steps than the sending switch, as in the case when repeating from a slower to a faster channel. To equalize the total number of steps taken by the two switches, and to prevent the sending switch from overtaking and passing the receiving switch, the latter switch is caused to double step at times under control of the circuit now to be described.

Each of the rotary switches 39 and 5B is provided with a sixth bank of contacts designated, respectively, Al and GI, contacts of bank 4| being connected to those of bank 6! as follows: The first contact of bank 5| to the fifth contact of bank 61; the second contact of bank ll to the first contact of bank 6!; and so on, in other words each bank contact of the sending switch being connected to the next bank contact ahead on the receiving switch. As a result of this method of connection the wiper of the sixth bank of contacts SI of the sending switch is connected to the wiper of the sixth bank of contacts 4! of the receiving switch only when the sending switch is one step behind the receiving switch.

When it occurs that the sending switch is but one step behind the receiving switch, battery is connected through resistance 32 and conductor 33 to the wiper of bank 6i of switch 58, and thence to the wiper of switch bank ll of switch 39, and through conductor 3 5 to the upper armature of relay 23. When, thereafter, the receiving distributor sixth pulse causes relays 2'5 and 23 to operate, relay 25 operates magnet 28 as previously described and at the same time relay 23 causes operation of relay 35 due to the completion of the circuit just previously described from the upper armature of relay 23, to contact B of that relay and through the winding of relay 35 to ground. When relay 25 releases, magnet 28 also releases and steps the receiving switch wipers ahead one step in the same manner as has been previously described. When magnet 28 releases, however, a circuit is completed through resistance 32 and conductors 33 and 42, contact A and upper armature of magnet 28, conductor 63, contact A and upper armature of relay 35, and the winding of relay 35 to ground. This locking circuit retains relay 35 operated.

Relay 23 is slightly slow to release, as has been mentioned hereinabove, so that it does not release until after magnet 28 has released. When the relay 23 releases it closes a circuit through its contacts D and contacts B of relay 35 to the winding of stepping magnet 28 which causes magnet 28 to operate again. Upon such operation the locking circuit for relay 35 is opened at contact A of stepping magnet 23 and thus relay 35 releases and, in turn releases stepping magnet 28 causing switch wipers of switch 3-3 to take a second step.

When the receiving rotary switch wipers take a double step as just described, in order to keep ahead of the sending switch wipers, the receiving switch wipers pass over contacts of the banks 36 through 60 connected to one group of five condensers. These five condensers are not charged at this time due to the fact that the relays I6 through 29 are not operated when the second stepping action occurs. This results in effect in storing idle signals on one group of condensers. Thus when the sending switch wipers of the banks 56 through 60 make connection to this group of condensers, no one of the relays 16 through will be operated and consequently an idle signal will be transmitted to the second line section during the next revolution of the sending distributor.

Stopping the rotary switch when idle When signals from the transmitting station stop completely, the five receiving-selecting relays I6 through 20 remain unoperated, and since as has been described sixth pulse control relay 25 is operated through the parallel connected contacts of these selecting relays, relay 25 does not operate. Due to the non-operation of this relay the receiving rotary switch stops.

The sending switch, however, continues to operate until the wipers are one step behind those of the receiving switch, when a circuit previously described is closed through the wipers of the sixth contact banks 4| and 6| of the receiving and sending switches to the upper armature of relay 23. Due to the fact that relay 23 is not operated, this circuit is extended through contact A of this relay and conductor 4 to the winding of relay 95 and thence to ground. Relay 96 (Fig. 2) is thus caused to operate and in so doing opens the circuit to the sending stepping switch 88 (Fig. 1) at its contacts B,'stopping the sending switch. The last character signal stored on the condensers will have been transferred to the sending relays on the last step of the sending switch. Relay BI will continue to operate, assuring the final release of relays I6 through 80 after the transmission of the last character signal. However, due to the operation of relay 96 the continued operation of relay 8| will be ineffective to cause stepping of the rotary switch.

Re-starting When character signals (i. e. signals other than idle signals) are again received, relays I6 through 20 (Fig. 1) will again operate, closing the circuit for relay 25. Since the sending switch is only one step behind the receiving switch at this time, relays 23 and 35 operate when the first character signal is received and the receiving'switch 30 takes a double step after which it continues to operate in the normal manner. This double stepping action always takes place after the circuit has been idle, thus introducing an idle signal after the first character signal transmitted from the repeater. When relay 23 operates it releases the relay 96 so that the stepping action of the sending switch 50 starts immediately after the stepping action of the receiving switch 30.

Indicating lamp An indicating lamp is provided to show when the repeater is operating normally, and when idle signals are being received by and passed through the repeater. This lamp is shown in Figure 1 and designated 80!. The lamp is in a circuit which leads from battery through resistances 32 and I02, over conductor I03 to the lamp IOI, and thence over conductors I04 to I to ground. Thus when the repeater is operating normally, the lamp is lighted except, however, that each time that the receiving switch 30 double steps, the winding of relay 35 is shunted across the lamp causing it to be extinguished momentarily. Thus in normal operation the lamp will light steadily except that it will blink occasionally at uniform intervals. However, when the circuit is idle and relay 96 is operated, as has been described above, the winding of this relay is shunted across the lamp and therefore the lamp is extinguished, such a steady state indicating that the repeater is receiving idle signals only. Thus the signal lamp mentioned serves to indicate whether the repeater is idle or operating in a normal manner.

017 speed alarm signal As has been stated hereinabove, a condition is possible wherein signals are received at a rate sufiiciently in excess of the transmitting speed so that the storage capacity of the repeater is exceeded. A lamp is provided to indicate when this condition exists, the lamp being shown in Figure l and being designated I06. The circuit which controls this signal involves both the receiving and the sending relays. When the olfspeed alarm toggle switch I0! (Fig. 1) is closed, a circuit is completed from battery through resistance I08, lower winding of electro-polar relay I09, conductor H0, the upper blade of switch I01, and conductors I04 and I05 to ground. The construction of the so-called electro-polar relay I09 is such that it has substantially the same characteristics as a polar relay and is operable on a very short current impulse. This relay has an iron collar around the center portion of its core which is connected to an outer pole piece or back-stop in front of the armature. Current flowing through the winding due to closure of the circuit previously described magnetizes the outer pole piece as well as the core, and since the armature is between the pole piece and the core end it is not pulled strongly in either direction and the pressure of the contact springs will normally hold it in the released position. If while this winding is energized a short current impulse is sent through the other or operating winding, it will increase the pull due to the core and the armature will pull up, but since the armature is closer to the core than to the outer pole piece, it will remain operated even though the current impulse through the operating winding ceases until the magnetizing winding is opened by opening the toggle switch I01.

The receiving selecting relays I6 to 20 normally release immediately after relay 23 operates, as has been described, but when the toggle switch I0! is closed, a ground is connected through conductors I05, I04, lower blade of toggle switch I 01, conductor III, resistance H2, contact C of relay 25, conductor 22, contacts A of relays I6 through 20, and the windings of those relays, to battery. Thus the receiving-selecting relays are held operated until relay 25 releases. However, the resistance II2 so reduces the strength of the locking current that the receiving-selecting relays I6 through 20 will release quickly upon the release of relay 25. This release time is so small that the relays I6 through 20 will be released before relay 23 can release to re-close their locking circuits. There is, therefore, a brief interval after relay 25 releases when battery is connected through the upper or operating winding of electro-polar relay I09, the circuit therefor being as follows: From battery through conductor II 3, the operating winding of relay I09, lower armature and contact E of relay 23, conductor H4, and through contacts C and cooperating armatures of any relay or relays of the group I6 through 20 which have been operated to the wipers of the receiving rotary switch 30 and thence to particular ones of the groups of condensers 42 through 46, the condensers of the group being dependent, of course, upon the position of the wipers of switch 30.

Since the condensers charge very quickly when relay 25 first operates, they will be completely charged when the release of relay 25 removes the short-circuit from the operating winding of relay I89. Since these condensers are completely charged, no current will flow through the operating winding of relay I09 and during the normal operation of the repeater relay I69 will not operate. If, however, the condition mentioned above, that is, the condition of excess character signal speed occurs, the receiving rotary switch will not stop sufficiently often with the result that the wipers of receiving rotary switch 30 will overtake the wipers of sending rotary switch 56. When this occurs contacts C of the receiving relay I through will be connected directly through the wipers of the corresponding banks of the receiving switch 3%) and the wipers of the similarly corresponding banks of the sending rotary switch 551, to the windings of sending relays IS through 80, respectively.

Thus the circuit described above, through the operating winding of relay I99, will be completed and current will continue to flow operating relay I09 at the time when relay releases. Relay I09 will close a circuit at its contacts A leading through conductor H5 to signal lamp H6 and thence over conductors I84 and I05 to ground. The lamp will, of course, remain lighted until relay IE9 is released, by opening the toggle switch I01.

In addition, operation of relay I89 will close a circuit leading from battery through bell II'I, conductor H8 and contacts B of relay I09 to ground. This will bring about operation of the bell III, which bell is common to all the multiplex channel repeaters in an omce and operates whenever any one of these repeaters is off speed. Of course the bell ceases to operate when the toggle switch I91 of the repeater which is off speed is opened.

Stop signal It is necessary when the multiplex terminal sets of one line section are being synchronized, or a line section is out of service for any other reason, to send a stop signal from the repeater over the other line section in order to notify the operator not to send over the through channel, although of course operation of the non-repeated channel of the terminal sets on the second line section may be continued. The letters signal is utilized as a stop signal since it can be easily recognized and does not cause the printer to record characters repeatedly. When channel repeaters of the type herein disclosed are used, there is no connection between the two line sections except that through the repeaters. Therefore the repeaters themselves must be arranged to transmit this signal when required. As indicated, the sending of this letters stop signal involves the sending sides of the two channel repeaters operating to repeat signals in opposite directions from one line section to the other.

Referring now to Figure 2, the stop signal circuit will be described, it being understood that the single sending side will be utilized as an illustration, the circuits being through it, and (by referring to it) through the sending side of the associated repeater.

Under normal operating conditions relays SI of the two repeaters are continually operated by impulses from the corresponding sixth pulse contacts 82. These contacts are closed and the relays consequently operated for a short period during each revolution of the distributors, but are released during the remainder of each revolution. The slow to release relays 84 are operated through contacts E of relays 8| and therefore current flows through their windings most of the time. When the windings of these relays 84 are opened, the relays nevertheless remain operated due to their slow to release characteristics, but will release in about one-half second. Thus if the relays 8I be operated for a time greater than onehalf second, the relays 8 will release. Relays BI may be held open by operating the transmitter locking switch 83 to close contacts A thereof.

\Vhen the transmitter switch 83 associated with one repeater is operated relay 34 of that repeater will release after the half-second interval mentioned, and a circuit will then be completed leading from ground through contacts B of relay 84, and over conductor I26, to contacts A of relay 84 of the other repeater of the pair, and thence through relay I2! (Fig. 2) to battery. This will cause relay I2I of the second repeater to operate and the operation of this relay will connect spacing battery directly through its contact to the first four transmitting segments 9| through 94 and marking battery to the fifth segment 95, thereby sending the letters signal repeatedly to the distant terminal, to advise the operator thereat of a failure in the other or first line section.

The release of relay 84 of the first repeater of the pair, as described, will also apply ground to conductor I22, thus short-circuiting the operating winding of relay 25 (Fig. l) thereby stopping the rotary switch 30 of the first repeater and transmitting idle signals from this repeater over the first line section. Of course if the transmitter locking switch 83 of the other repeater, that is, the second repeater, had been operated, then the letter signals would have been sent back over the first line section and the idle signal would have been sent out from the repeater on the second line section.

If the locking switches 83 of both associated repeaters had been operated, then relay 84 of both repeaters would have been released and therefore neither of the relays I2I would be operated. In this manner idle signals would be transmitted from the repeaters over both line sections. This condition would obtain, for example, if both circuits were being lined up, that is, synchronized and phased.

Transmitter control mechanism As has been stated above, when a channel repeater is in service it is necessary that the effective signal speed of transmission from the distant station be reduced to a point at least as low as, and preferably lower than the speed at which signals are being transmitted over the line section into which the repeater sends its signals. For this purpose the circuit and mechanism shown in full lines at the right of Figure 3 is supplied. This circuit operates in conjunction with the usual transmitter and auto speed control shown in dash lines at the left of Figure 3. In order that the operation of the speed reducing unit be clear, the normal mode of operation of the transmitter and auto stop unit will first be briefly described.

When the sixth pulse contacts of the transmit ting distributor close, circuits are completed through these contacts from battery to the transmitter operating magnets I3I, to relay I32, and through contacts I33 controlled by the tape lever I34 to relay I35. This results in operation of the transmitter magnets and of relays I32 and I35. A circuit which would otherwise be completed at contacts A of relay I32 to cause operation of the transmitter locking magnets I36, is broken at contacts A of relay I35 and therefore the only effective operation is that of the operating magnets I3I.

The transmitter continues to step as the sixth pulse contacts I30 are closed until such time as the perforated tape, normally extending in a loop below the tape lever I34, becomes taut, at which time contacts I33 are opened and the next sixth pulse operates only relays I32 and transmitter operating magnets I3I, leaving relay I35 deenergized.

As a result of this the circuit is completed through contacts A of relay I32 and transmitter locking magnets I36. This causes the operating magnets as well as the locking magnets to be energized, and locks the transmitter so that no further operation can occur. When the tape lever I 34 is restored to its normal position, the next following closure of the sixth pulse contacts I 30 will again energize relay I35 and break the locking circuit to the operating magnets I36 thereby permitting the transmitter to resume normal operation.

In adapting this transmitter for use in conjunction with the speed reducing unit, a jack I? is inserted in the circuit to relay I35. Normally the circuit is closed through the jack due to completion of the circuit through the tip and cooperating make contacts of the jack. However when the plug I38 is inserted in the jack this circuit is broken and instead the circuit from the tape lever contacts I33 leads through the sleeve of jack I37 to the sleeve of plug I38 and thence over conductors I 40 and I II to the lower rotor of a commutator type switch I 50, and when the switch is in any position other than its off position, through that rotor and conductor I42 and through the lower winding of relay I43 and conductor I44, and through plug and socket connection I45 to ground.

In addition the circuit extends over conductor I4I to a number of contacts of the rotary switch I5I. Among these contacts is the first one on which the switch wiper is resting in the position shown in the drawings. For this position, therefore, the circuit is extended through the switch wiper to conductor I46 and through the tip of plug I33 and tip of jack I3! to relay I35. Thus the relay I 35 will receive an impulse from the sixth pulse contacts I30 and the transmitter and auto step unit will operate in normal manner. In addition, relay I 4-3 will receive an impulse and will operate, and once operated will be locked in operated position over a circuit extending from battery through plug connection I45 and over conductors I 47 and I48, resistance I 52, to contacts A of the stepping magnet I53 of rotary switch I5I, thence through the winding of stepping magnet I53 to conductor I54, and through closed contact B of relay I43 to conductor I44 and ground. Operation of relay I43 in addition causes closure of a locking circuit for that relay, which circuit may be traced as follows: from battery through the plug connection I45, conductors I47 and I55, resistance I56, upper winding of relay I43, and contacts A of that relay, and thence over conductor I51 to contacts B of stepping magnet I53, and by way of conductors I58 and I44 to ground.

Due to the circuits just described, relay I43 looks in its operated position and thus assures complete operation of stepping magnet I53, the circuit through locking winding of relay I43 being broken at contacts B of stepping magnet I53 when that magnet has completed its operation. Thus even though the sixth pulse be extremely short, the operation of stepping switch I5I is assured. Contacts A are supplied for stepping magnet I 53 so that though the operating current for that magnet passes through resistance I52 only, and is therefore fairly great, holding current for the magnet passes through resistance I52 and resistance I54 and is therefore of lesser value.

Each time that the sixth pulse contacts are closed, stepping switch I5I is advanced one step. As shown in the drawings, with the control handle set to its eighth position, during the first two steps of movement the tape transmitter will operate in normal fashion and the tape therein will be advanced two steps and two character signals sent from the transmitter to the sending transmitter and to the line. When the wiper rests on its third contact, however, it will be noted that no circuit is completed through any of the commutators of switch I55 or otherwise to relay I35, and consequently the transmitter is locked until succeeding closure of the sixth pulse contacts I34. However the wiper of the rotary switch I5I steps to its fourth position and thus when the next closure of the sixth pulse contacts I 38 occurs a circuit is completed leading from battery through these contacts over sleeve of jack I 37 and sleeve of plug I38 and conductors I 46 and I4I to the commutator second from the top in Figure 3, to conductor IIiI, and thence to the fourth contact of rotary switch I 5|, thence to the wiper of that switch and over a circuit previously described, to relay I35.

As has been described, this releases the locking magnets I36 and permits the transmitter to step the tape ahead a single step. Without tracing the circuits in any greater detail, it will be obvious that the transmitter is locked and caused to send blank or idle signals at certain periods dependent upon the setting of the commutators of switch I5I which commutators are mounted on a common shaft and controlled by the knob, shown, together with its cooperating scale at I52. By reference to the chart of Figure 4 it will be seen that when the switch is in its eighth position as shown, eight of every twenty-four signals sent from the transmitter are blanks, these being as follows: third, sixth, ninth, twelfth,

;fifteenth, eighteenth, twenty-first and twentyfourth. By comparing the connections of the commutator switch I5I of Fig. 3 with the chart, Fig. 4, it will be obvious that the various commutators are so laid out and the connections so made that for each position of the switch the transmitter is caused to send a different number of blank signals in each group of twenty-four signals. Thus it is shown by the chart. that when the switch is set at seventh position, seven blank signals are present in each twenty-four signals transmitted, and when in the sixth position six blank signals are transmitted for each twentyfour signals.

When the switch handleIfiZ is rotated to its off position, the fifth commutator of the switch (counting from the top Fig. 3) is so positioned that a circuit is extended from conductor I4] to conductor I46, thereby causing the transmitter and autostop unit to operate in the same fashion as if no speed reduction unit were used. This is done merely for convenience and so that it is unnecessary to remove plug I38 from jack I31. Also at this time the circuit to operating winding of relay I43 is broken at the lowermost commutator of switch I50, thereby preventing operation of relay I43 or of the stepping switch II, the speed reduction unit being completelg, idle when the switch is in the off position.

Monitoring arrangements In the foregoing, mention has been made of the monitoring arrangements which provided means not only for checking the operation of the repeater, but also for talking from the repeater to the distant terminal station. This monitoring equipment consists of a tape transmitter and auto-stop unit identical to the one just previously described in connection with the speed reduction unit, together with a test distributor, that is, a distributor having both sending and receiving segments and well known in the art. In addition the monitoring equipment includes a multiplex printer and a multi-contact switch for rearranging the circuits in five different manners, as will be described.

In the drawing, Figure 5, the transmitter and auto-stop unit are enclosed in dotted lines and. are designated I10, the unit being supplied with a jack exactly similar as respects circuit arrangements with the jack I31 of Figure 3. The five sending segments of the test distributor are indicated at HI and are connected to the contacts of transmitter I10. These contacts are in turn strapped together and to the two leads I12 and I13, each of which connects to one of the windings of the differential polar relay I14, after which the two circuits join and are grounded. Relay I14 corresponds to the printer relay of an ordinary multiplex terminal set. The single armature of this relay I14 is grounded and the contacts thereof are connected to the receiving segments I15 of the test distributor, the contact A being connected to the first four of these segments and contacts 13 to the fifth segment, in order to provide for signal reversals during transmission of idle signals, as has been mentioned hereinabove.

The multiplex printer mentioned above is indicated in the drawing (Fig. 5) by showing the five magnets thereof designated I16 in the drawing. In addition to the equipment already mentioned, there are provided two plugs I11 and I80, plug I11 being adapted for insertion in the corresponding plug receptacle I18 on the output side of the repeater (see Fig. 2), and plug I80 being adapted for insertion in the corresponding plug receptacle I8I on the input side of the repeater (see Fig. 1).

When the switch I82 which comprises a plurality of contact arms settable in unison to any one of five positions is in its third position, as shown in Figure 5, circuits are completed which serve to test the transmitter I10. This arrangement is a common one provided in large telegraph ofiices so that transmitters and printers may be tested. Briefly when the switches are in this third position signals are sent from the transmitter contacts and received on the polar relay I14, these signals being then transferred to the receiving contacts and thence over conductors I83 through I81 on the first five banks of switch I82 to the five selecting magnets of the printer, and thence to battery and ground. The sixth pulse is supplied to the printer through a circuit extending through the sixth pulse segments of the receiving distributor and thence over conductor I88 to the sixth pulse magnet oi the printer. It will be seen that these circuits are entirely local and that therefore the operation of the various units involved in the system may be tested by simply feeding a test tape through the transmitter.

If it is desired to check on the signals received by the repeater, switch IE2 is set so that its switch arms rest on the first contacts. In this case a number of circuits is completed which may be traced as follows: From segment II of the receiving distributor, over conductor I90 to a terminal of plug receptacle IBI (Fig. l), and thence to the corresponding terminal pin of plug I87] to conductor I9I through contacts A of relay 299, to conductor I92 and thence to the first selecting magnet of the printer, and to battery and ground. It may be seen that with such an arrangement the first printer magnet I15 operates in parallel with the first receiving selecting relay I6 (Fig. l). The remaining printer selecting magnets I16 are connected in parallel with the remaining receiving selecting relays I1 through 20 in the same manner so that the first pulse selecting relay operates in parallel with the first pulse selecting magnet of the printer, the second pulse selecting relay operates in parallel with the second pulse printer magnet. etc. The sixth pulse control magnet 25 of the channel repeater (see Fig. 1) is provided with contacts A which contacts are connected through the plug receptacle I8I to conductor I93 (Fig. 5), to the winding of relay 200, and thence through the sixth switch bank and corresponding wiper arm to the sixth pulse magnet I16 of the printer.

Thus upon operation of the sixth purse (:Uutrol relay 25, relay 290 is operated and breaks the circuit through its contacts A, B, C, D and E, leading from the distributor segments to the printer magnets. This relay 200 is supplied in order to prevent the printer magnets I16 from acting as high inductance shunts on the receiving selecting relays It through 20, and thus to assure that these relays do not have a slow to release characteristic while the monitor printer is in use.

It will be seen that due to the circuits just described the monitor printer is operated in parallel with the receiving selecting relays and thus the received signals are printed by the monitor printer as a check upon line conditions including of course the synchronization and phasing of the terminal multiplex distributors.

When the arms of switch I82 are set to their second position, the monitor set of Figure 5 is adapted to check the outgoing signals from the channel repeater. In this instance a typical one of the selecting magnet circuits, i. e. the circuit for the first printer magnet, can be traced as follows: From battery through the first magnet I16, thence through the first upper wiper arm and cooperating second contact of switch I82, to conductor I84, thence through plug I11 and receptacle I18 to conductor I95 (Fig. 2), thence through contacts B of relay 16, and contacts D of sending sixth pulse relay SI, to ground. Since the other selecting magnets I16 of the printer are connected in similar fashion to contacts B of the remaining sending selecting relays 11 through 80, it will be apparent that signals emanating from these relays are transmitted to the printer selecting magnets to properly set the printer for printing the corresponding character.

The sixth pulse for the printer is supplied over relays I through 25.

the following circuit: from battery through sixth pulse magnet I16, thence over the wiper and second contact of the sixth contact bank of switch I82, and thence over conductors I96 and I91 through the plug and plug receptacle I11 and I18, over conductor I98 (Fig. 2) to contacts B of the stepping magnet 88 of the sending rotary switch 50 (Fig. 1) Thus upon each step of the sending rotary switch the monitor printer receives a sixth pulse and prints the same character which is being sent to the line through contacts C and D of the sending-selecting relays 16 through 80. When arranged in this fashion the monitor set gives a check on the outgoing signals from the repeater.

When the switch I82 is set with its wiper arms on the third contacts of the various switch banks, the monitor set is adapted for local testing of transmitters, printer, etc., as has already been mentioned.

When switch I 82 is set with its wiper arms on its fourth contacts the circuit is arranged for talking with a distant terminal. When so used the plug I11 is inserted in the receptacle I18 of the channel repeater which is repeating signals in one direction between the two line sections, while the plug I80 is inserted in the receptacle I8I of the repeater operating to repeat signals in the opposite direction between the two line sections.

With the understanding that the plugs are inserted as described above, it will be seen that signals from the transmitter I 10 are sent through the test distributor over conductors I83 through I81, and through the wiper arms of the first five j of the lower contact banks of switch I82, and through plug I80 and receptacle I8I to the operating windings of receiving selecting relays I6 through 20, thereby causing the operation of these relays in accordance with the signals sent from the transmitter I10.

It will be understood of course that the receiving multiplex distributor of Fig. 1 is in this instance disconnected so that ground is not supplied through its segments to any of the selecting In effect, therefore, the transmitter I10 and test distributor is substituted for the receiving multiplex distributor and signals from the transmitter I10 are sent through the repeater to the distant terminal station. At

the same time, due to the setting of the switch I82 and the insertion of plug I11 in receptacle I18 of the repeater operating in the opposite direction, signals which are received through that repeater are impressed upon the printer selecting magnets I16 thereby making it possible to receive signals from the same distant terminal station to which signals are being transmitted.

It will be clear by reference to Figure 5 that the sixth pulse to the first repeater is supplied from the sixth pulse contacts of the sending side of the test distributor over the wiper arm of the sixth contact bank in the lower row, and thence over conductor 2M and through plug I 80 and receptacle IBI to the operating winding of sixth pulse control relay 25 (Fig. 1), thus substituting the sixth pulse contacts of the test distributor for the sixth pulse contacts 24 of the multiplex receiving distributor.

It will likewise be clear that the sixth pulse for the sixth pulse magnet I16 of the monitor printer is supplied from contacts B of stepping magnet 88 in the same manner as has been described above in connection with monitoring on the sending side of the repeater.

When the monitoring switch I82 is set in its fifth position, circuits are set up for testing a single multiplex channel repeater. In this instance signals from the transmitter I11) are substituted for signals from the receiving distributor of Figure 1 in exactly the same manner as was described above in connection with talking over the repeater. However, instead of plugging plug I11 into the receptacle I18 of the repeater operating in the opposite direction, it is plugged into the receptacle of the same repeater. Therefore the signals received on the monitor printer are the same signals which are passing to the line and should be, if the repeater is operating properly, the signals which were supplied to the repeater from the transmitter I111. Since the circuits are identical tothose just described in connection with talking, with the exception that the plug I11 is inserted in the receptacle I18 of the same repeater, and with the exception that the sixth pulse from the sending segments of the test distributor is supplied not only to relay 25 as in talking but also to sending sixth pulse relay BI (Fig. 2) these circuits will not be traced again.

It will be noted that the transmitter I16 of the monitoring set is supplied with a jack similar to that of the transmitter of Figure 3. This is supplied in order that the speed reduction unit of Figure 3 may .be utilized with the monitoring set for talking since, as will be obvious, the effective signal speed must be reduced in some instances and it is simpler to reduce it with the aid of this unit than to readjust the test distributor.

While I have described a preferred embodiment of my invention, and have described various elements of my invention in combination with various other elements, it will be understood that other forms of the invention may be utilized, and that some elements might be utilized without utilizing all. Therefore it is understood that the scope of the invention is not to be limited by the foregoing specification, .but is, on the other hand, to be limited solely by the appended claims.

What is claimed is:

1. In a repeater for repeating signals from a channel of a multiplex receiving distributor associated with one line section and operating at a relatively low efiective signal speed, to a channel of a multiplex sending distributor associated with another line section and operating at a relatively high eifective signal speed, in combination, means for receiving character signals from said receiving distributor, a group of signal storing means, means for transferring successively received character signals to successive ones of said group of storage means, means for preventing the transmission of received inefiective signals to said storage means, means for transferring said stored effective character signals to the multiplex sending distributor of the second line section at a rate dependent upon the speed of said sending distributor, and means under the joint control of said two transferring means to cause said first mentioned transferring means to operate twice in rapid succession whenever said second transferring means lags said first transferring means by a single step of movement.

2. In a device for repeating signals from a channel of a multiplex circuit operating at'a particular efiective signal speed to a channel of another multiplex circuit operating at the same effective signal speed but a different over-all signal speed, in combination, means for receiving effective and ineffective code impulse signals from the first multiplex circuit, a plurality of groups of means for storing said code signals, means for transferring effective code impulse signals from said receiving means to successive groups of storing means, said transferring means comprising a rotary switch and means to operate the latter through one step of movement upon reception of each effective code signal, means for sending code impulse signals to said second mul tiplex circuit, and means for transferring signals successively from said groups of storage means to said sending means, said transfer means comprising a second rotary switch operable step by step at a rate determined by the over-all speed of said sending means, and means under the joint control of said first and second rotary switches to cause said first switch to perform two stepping operations whenever said second switch attains a position one step behind said first switch, said double stepping operation serving to insert ineffective signals into the train of effective signals sent from said sending means, to thereby render the over-all rate of sending equal to the predetermined over-all speed of said signal sending means.

3. In a multiplex telegraph circuit including a repeater for repeating signals from a channel of a first line section to a channel of a second line section operating at an over-all signal speed less than that of said first line section, means for reducing the effective signal speed on said first line section to a speed less than the overall signal speed of said second line section, said means comprising in conjunction with a multiplex tape transmitter a rotary switch operable step by step under control of the transmitter operating pulse, and means under control of said rotary switch for periodically preventing operation of said tape transmitter whereby idle signals are sent over the first line section thereby reducing the effective signal speed to a point less than the over-all signal speed of the second line section, and means in said repeater for periodically inserting idle signals sufficient in number to bring the over-all speed of transmission on the second line section to the normal operating speed of that line section.

4. In a speed reducing unit for reducing the effective signal speed of a multiplex transmitter, in combination, a rotary switch of the step by step type, means to operate said switch upon reception of each transmitter impulse, and connections through certain of the contacts of the wiper of said switch to the locking mechanism of said transmitter to cause periodic operation of said locking mechanism whereby said transmitter periodicall sends a blank signal.

5. In a speed reducing unit for reducing the effective signal speed of a multiplex transmitter, in combination, a rotary switch of the step by step type, means to operate said switch upon reception of each transmitter impulse, a manually settable switch, connections through said switch to the contacts of said rotary switch, and a circuit leading from the wiper of said switch to the locking mechanism of said transmitter to cause periodic operation of said locking mechanism at intervals dependent upon the setting of said manually settable switch.

6. In a mutiplex channel repeater of the type described, means for receiving-multiple impulse code signals from one line section, means for storing a limited number of said signals, means for transmitting said signals to a second line section and indicating means operable when signals are received more rapidly than transmitted during a period sufiicient to exceed the storage capacity of said storing means.

'7. In a multiplex channel repeater of the type described, signal receiving means, signal storing means, a receiving rotary switch for transferring signals from said receiving means to said storing means, signal transmitting means, a sending rotary switch for transferring signals from said storage means to said transmitting means, means for causing said receiving and sending rotary switches to maintain a relationship within predetermined limits such that said sending switch normally lags said receiving switch by at least one step of movement but not by the number of steps of movement comprising a complete rotation, and means operable when said receiving switch comes into phase with said sending switch to operate an alarm signal.

8. In a multiplex channel repeater adapted to repeat signals from a receiving multiplex distributor to a sending multiplex distributor operating at a difierent speed, in combination, signal impulse receiving means, a control relay operable under control of the receiving distributor, means to prevent operation of said relay unless one or more of said signal receiving means have operated, means controlled by said control relay for locking said signal receiving relays in operated position, signal storing means, a rotary receiving switch normally connected to contacts of said control relay through contacts of said receiving relays to transfer signals to said storage means in accordance with the signals received, transmitting means, a rotary switch for connecting said storage means with said transmitting means, a signalling means, and means comprising a relay shunted around the contacts of said control relay and normally deenergized for indicating when said two rotary switches are in phase due to said first switch operating more rapidly than said second switch for operating said signalling device.

9'. A multiplex channel repeater comprising means for receiving signals from one line section, means for transmitting signals to another line section, means for storing signals, means for transferring signals from said receiving means to said storing means, means for trans ferring signals from said storing means to said sending means, means for operating said two transferring means at different instantaneous rates, said second transferring means normally operating more rapidly than said first transferring means, and means operable when said first transferring means overtakes and is in phase with said second transferring means for indicating such abnormal condition.

10. In a multiplex channel repeater, in combination, means comprising a group of relays for receiving multi-impulse code signals, a plurality of groups of signal storage means, means for connecting said receiving relays to successive groups of said storing means, a control relay operating repeatedly at a predetermined rate to actuate said signal storing means connected with operated receiving relays, signal transmitting relays, means for connecting said signal transmitting relays to successive groups of said signal storing means at a different and normally equal rate to the connection of said signal receiving means, said two connecting means being normally out of phase with the first leading the second, an indicating relay and a circuit completed from said control relay over said receiving relays and said two connecting means to said sending relays when said first connecting means reduces the lead of said second connecting means to'zero,'said completed circuit effectively removing a shunt from the winding of said indicating relay, said relay thereby operating to give an indication of the abnormal in phase relationship of the said two connecting means.

11. In a multiplex channel repeater, in combination, means comprising a group of relays for receiving multi-impulse code signals, a plurality of groups of signal storage means, means for connecting said receiving relays to successive groups of said storing means, a control relay operating repeatedly at a predetermined rate to actuate said signal storing means connected with operated receiving relays, signal transmitting relays, means for connecting said signal transmitting relays to successive groups of said signal storing means at a difierent andnormally equal rate to the connection of said signal receiving means, said two connecting means being normally out of phase with the first leading the second, a lamp for indicating an off speed condition, a relay for operating said lamp, and a circuit completed from said control relay over said receiving relays and said two connecting means to said sending relays when said first connecting means reduces the lead of said second connecting means to zero, said completed circuit efiectively removing a shunt from the Winding of said indicating relay, said relay thereby operating and lighting said lamp to indicate the off speed condition.

12. In a multiplex channel repeater adapted to repeat signals from a receiving multiplex distributor to a sending multiplex dictributor operating at a higher effective signal speed, in combination, signal impulse receiving relays, a control relay repeatedly operable under control of the receiving distributor at a rate equal to the effective signal speed, a plurality of groups of signal storing means, means for connecting said groups of signal storing means successively to said signal receiving relays, said control relay having a contact for supplying current to said signal receiving means to thereby effect transfer of received signals to said storing means at a rate equal to the efiective signal speed of the receiving distributor, signal impulse sending relays, means to connect said sending relays successively to said groups of storage relays at a rate determined by the sending distributor speed,

and an alarm signal operable under control of said control relay when the efiective signal speed of reception exceeds the speed of transmission.

13. In combination with a pair of channel repeaters of the type described, and interconnecting two multiplex circuits for repeating in both directions, means for stopping transmission from one of said repeaters, and means under control of said stopping means for causing said second repeater to transmit stop signals back over the line.

14. In combination with a pair of channel repeaters of the type described interconnecting channels of two multiplex circuits for repeating messages in both directions, means comprising a manually operable switch and a slow releasing relay at each repeater for stopping transmission from that repeater, a relay at each said repeater connected through contacts of said slow releasing relay to the corresponding relay of the other repeater when said slow releasing relay is operated, and to ground when said slow releasing relay is released, and means operated by said second relay at each repeater for causing that repeater to repeatedly send a stop signal over its outgoing multiplex channel.

15. In a multiplex channel repeater, in combination, means for receiving signals over a multiplex channel at a predetermined speed, means for locking and subsequently releasing said receiving means, means for storing said signals, means for sending stored signals to another multiplex channel at a difierent predetermined speed, and means for monitoring the received signals, said means comprising a multiplex printer having its selecting magnets connected in parallel with said means for receiving signals, and means for breaking all said parallel circuits simultaneously to prevent the inductance of said printer magnets from preventing release of said repeater signal receiving means.

16. In a multiplex channel repeater, in combination, means for receiving signals over a multiplex channel at a predetermined speed, means for storing said signals, means for sending stored signals to another multiplex channel operating at a difierent channel speed, and means for monitoring the operation of said repeater, said means comprising a multiplex transmitter and a multiplex distributor connected to transmit signals to said repeater receiving means, and a multiplex printer adapted to receive signals 'from said repeater transmitting means.

GILBERT S. VERNAM.

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