CHAPTER XXXI

THE AUTOMANUAL SYSTEM

Two systems of telephony are now in common use in this country--the manual system and the automatic. With the growth of the automatic, and the gradually ripening conviction, which is now fully matured in the minds of most telephone engineers, that automatic switching is practical, there has been a growing tendency toward doing automatically many of the things that had previously been done manually. One of the results of this tendency has been the production of the _automanual_ system, the invention of Edward E. Clement, an engineer and patent attorney, of Washington, D. C. In connection with Mr. Clement's name, as inventor, must be mentioned that of Charles H. North, whose excellent work as a designer and manufacturer has contributed much toward the present excellence of this highly interesting system.

=Characteristics of System.= The name "automanual" is coined from the two words, automatic and manual, and is intended to suggest the idea that the system partakes in part of the features of the automatic system and in part of those of the manual system.

We regret that neither space nor the professional relation which we have had with the development of this system will permit us to make public an extended and detailed description of its apparatus and circuits. Only the general features of the system may, therefore, be dealt with.

The underlying idea of the automanual system is to relieve the subscriber of all work in connection with the building up of his connection, except the asking for it; to complicate the subscriber's station equipment in no way, it being left the same as in the common-battery manual system; to do away with manual apparatus, such as jacks, cords and plugs, at the central office, and to substitute for it automatic switching apparatus which will be guided in its movements, not by the subscriber, but by a very much smaller number of operators than would be necessary to manipulate a manual switchboard.

=General Features of Operation.= A broad view of the operation of the system is this. The subscriber desiring to make a call takes down his receiver, and this causes a lamp to light in front of an operator. The operator presses a button and is in telephonic communication with the subscriber. Receiving the number desired, the operator sets it up on a keyboard in just about the same way that a typist will set up the letters of a short word on a typewriting machine. The setting up of the number on the keyboard being accomplished, the proper condition of control of the associated automatic apparatus at the central office is established and the operator has no further connection with the call. The automatic switching apparatus guided by the conditions set up on the operator's keyboard proceeds to make the proper selection of trunks and to establish the proper connections through them to build up a talking circuit between the calling subscriber and the called and to ring the called subscriber's bell, or, if his line is found busy, the apparatus refuses to connect with it and sends a busy signal back to the calling subscriber. The operator performs no work in disconnecting the subscribers, that being automatically taken care of when they hang up their receivers at the close of the conversation.

From the foregoing it will be seen that there is this fundamental difference between the automatic and the automanual--the automatic system dispenses entirely with the central-office operator for all ordinary switching functions; the automanual employs operators but attempts to so facilitate their work that they may handle very many more calls than would be possible in a manual system, and at the same time secures the advantages of secrecy which the automatic system secures to its subscribers.

=Subscriber's Apparatus.= One of the main points in the controversy concerning automatic _versus_ manual systems is whether or not it is desirable to have the subscriber ask for his connection or to have him make certain simple movements with his fingers which will lead to his securing it. The developers of the automanual system have taken the position that the most desirable way, so far as the subscriber is concerned, is to let him ask for it. It is probable that this point will not be a deciding one in the choice of future systems, since it already seems to be proven that the subscribers in automatic systems are willing to go through the necessary movements to mechanically set up the call. The advantage which the automanual system shares with the manual, however, in the greater simplicity of its subscriber's station apparatus, cannot be gainsaid.

=Operator's Equipment.= The general form of the operator's equipment is shown in Fig. 405. A closer view of the top of one of the key tables is shown in Fig. 406. As will be seen, the equipment on each operator's position consists of three separate sets of push-button keys closely resembling in external appearance the keys of a typewriter or adding machine. Immediately above each set of keys are the signal lamps belonging to that set.

The operator's keys are arranged in strips of ten, placed _across_ rather than _lengthwise_ on the key shelf. One of these strips is shown in Fig. 407. There are as many strips of keys in each set as there are digits in the subscribers' numbers, _i. e._, three in a system having a capacity of less than one thousand; four in a system of less than ten thousand; and so on. In addition to the number keys of each set is a partial row of keys, including what is called a _starting key_ and also keys for making the party-line selection.

The simplicity of the operator's key equipment is one of its attractive features. Fig. 408 shows one of the key shelves opened so as to expose to view all of the apparatus and wiring that is placed before the operator. The reason for providing more than one key set on each operator's position is, that after a call has been set up on one key set, a few seconds is required before the automatic apparatus controlled by the key set can do its work and release the key set ready for another call. The provision of more than one key set makes it possible for the operator to start setting up another call on another key set without waiting for the first to be released by the automatic apparatus.

=Automatic Switching Equipment.= A general view of the arrangement of automatic switches in an exchange established by the North Electric Company at Ashtabula, Ohio, is shown in Fig. 409. The desk in the foreground is that of the wire chief. This automatic apparatus consists largely of relays and automatic selecting switches. The switches are of the step-by-step type, having vertical and rotary movements, and an idea of one of them, minus its contact banks, is given in Fig. 410. The control of the automatic switches by the operator's key sets is through the medium of a power-driven, impulse-sending machine. From this machine impulses are taken corresponding to the numbers of the keys depressed.

=Automatic Distribution of Calls.= A feature of great interest in this system is the manner in which the incoming calls are distributed among the operators. From each key set an operator's trunk is extended to what is called a secondary selector switch, through which it may be connected to a primary selector trunk and calling line. When a subscriber calls by taking down his receiver, his line relay pulls up and causes a primary selector switch to connect his line with an idle local trunk or link circuit, at the same time starting up a secondary selector switch which immediately connects the primary trunk and the calling line to an operator's idle key set. If an operator is at the time engaged in setting up a call on a key set, or if that key set is still acting to control the sending of impulses to the automatic switches, it may be said to be busy, and it is not selected by this preliminary selecting apparatus in response to an incoming call. As soon, however, as the necessary impulses have been taken from the key set by the automatic apparatus, that key set is released and is again ready to receive a call. In this way the calls come before each operator only as that operator is able and ready to receive them.

=Setting up a Connection.= As soon as the key-set lamp lights, in response to such an incoming call, the operator presses a listening button, receives the number from the subscriber, and depresses the corresponding number buttons on that key set, thereby determining the numbers in each of the series of impulses to be sent to the selector and the connector switches to make the desired connection. The operator repeats this number to the calling subscriber as she sets it up, and then presses the starting button, whereupon her work is done so far as that call is concerned. If, upon repeating the call to the subscriber, the operator finds that she is in error, she may change the number set up at any time before she has pressed the starting button.

=Building up a Connection.= The keys so set up determine the number of impulses that will be transmitted by the impulse-sending machine to the selector and the connector switches. These switches, impelled by these impulses, establish the connection if the line called for is not already connected to. If a party-line station is called for, the proper station on it will be selectively rung as determined by the party-line key depressed by the operator. If the line is found busy, the connector switch refuses to make the connection and places a busy-back signal on the calling line.

=Speed in Handling Calls.= This necessarily brief outline gives an idea only of the more striking features of the automanual system. A study of the rapidity with which calls may be handled in actual practice shows remarkable results as compared with manual methods of operating. The operators set up the number keys corresponding to a called number with the same rapidity that the keys of a typewriter are pressed in spelling a word. In fact, even greater speed is possible, since it is noticed that the operators frequently will depress all of the keys of a number at once, as by a single striking movement of the fingers. The rapidity with which this is done defies accurate timing by a stop watch in the hands of an expert. It is practically true, therefore, that the time consumed by the operator in handling any one call is that which is taken in getting the number from the subscriber and in repeating it back to him.

TABLE XI

Total Time Consumed by Operator in Handling Calls on Automanual System

+-----------------------------------------------------------------+ | First 100 Calls | +-----------------------------------------------------------------+ |Longest Individual Period 12.40 seconds | |Average five longest Individual Periods 7.44 seconds | |Average ten longest Individual Periods 6.34 seconds | |Shortest Individual Period 1.60 seconds | |Average five shortest Individual Periods 1.92 seconds | |Average ten shortest Individual Periods 1.96 seconds | |Average Entire 100 Calls 3.396 seconds | |Hourly Rate at which calls were being handled 1060 | +-----------------------------------------------------------------+

+-----------------------------------------------------------------+ | Second 100 Calls | +-----------------------------------------------------------------+ |Longest Individual Period 7.60 seconds | |Average five longest Individual Periods 5.52 seconds | |Average ten longest Individual Periods 5.34 seconds | |Shortest Individual Period 2.00 seconds | |Average five shortest Individual Periods 2.04 seconds | |Average ten shortest Individual Periods 2.18 seconds | |Average Entire 100 Calls 3.374 seconds | |Hourly Rate at which calls were being handled 1067 | +-----------------------------------------------------------------+

+-----------------------------------------------------------------+ | Third 100 Calls | +-----------------------------------------------------------------+ |Longest Individual Period 5.40 seconds | |Average five longest Individual Periods 5.32 seconds | |Average ten longest Individual Periods 4.44 seconds | |Shortest Individual Period 1.60 seconds | |Average five shortest Individual Periods 1.65 seconds | |Average ten shortest Individual Periods 1.80 seconds | |Average Entire 100 Calls 3.160 seconds | |Hourly Rate at which calls were being handled 1139 | +-----------------------------------------------------------------+

Owing to the difficulty of securing accurate traffic data by means of a stop watch, an automatic, electrical timing device, capable of registering seconds and hundredths of a second, has been used in studying the performance of this system in regular operation at Ashtabula Harbor. The operators were not informed that the records were being taken, and the data tabulated represents the work of two operators in handling regular subscribers' calls. The figures in Table XI are given by C. H. North as representing the total time consumed by the operator from the time her line lamp was lighted until her work in connection with the call was finished, and it included, therefore, the pressing of the listening button, the receiving of the number from the subscriber, repeating it back to him, setting up the connection on the keys, and pressing the starting key.

It will be seen that the average time for each 100 calls is quite uniform and is slightly over three seconds. The considerable variation in the individual calls, ranging from a maximum of 12.40 seconds down to a minimum of 1.60 seconds, is due almost entirely to the difference between the subscribers in the speed with which they can give their numbers. These figures indicate that, in each of the tests, calls were being handled at the rate of more than one thousand per hour by each operator.

The test of the subscriber's waiting time, _i. e._, the time that he waited for the operator to answer, for one hundred calls made without the knowledge of the operator, showed the results as given in Table XII, in which a split second stop watch was used in making the observations.

TABLE XII

Subscribers' Waiting Time

+----------------------------------------------------------+ |Number of Calls Tested 100 | |Longest Individual Period 5.20 seconds | |Average 5 Longest Individual Periods 4.64 seconds | |Average 10 Longest Individual Periods 3.80 seconds | |Shortest Individual Period 1.00 seconds | |Average 5 Shortest Individual Periods 1.28 seconds | |Average 10 Shortest Individual Periods 1.34 seconds | |Average Entire 100 Calls 2.07 seconds | +----------------------------------------------------------+

The length of time which the subscriber has to wait before receiving an answer from the operator is, of course, one of the factors that enters into the giving of good telephone service, and the times shown by this test are considerably shorter than ordinarily maintained in manual practice. The waiting time of the subscriber is not, of course, a part of the time that is consumed by the operator, and the real economy so far as the operator's time is concerned is shown in the tests recorded in Table XI.