1974: electronic switching improves operator services by Eric Bierman

This TOPS history and description with SP1 is from 1974 and discusses the development of Traffic Operator Position System (TOPS) by Northern Telecom in Canada. It is a technical article by Eric Bierman formerly of Nortel, and reproduced here to gain a sense of that era in telecom Operator Services history. Where it was originally published is unknown to me at this time.

The giant leap
of historical note about TOPS for Operator Services is that it moved the operator station from a CAMA inspired console to a CRT and keyboard station. This was a big change in a work environment at the time, although the computer as we know it today is common, it was forward-looking then.


Eric Bierman received a B Eng in electrical engineering from McGill University, Montreal, in 1962, and later an M A Sc in computer science from the University of Waterloo. After graduating from McGill, he joined Northern Electric Company and worked on analog radio, data sets, and switching systems. The following year he moved to Bell-Northern Research and was engaged in the design of crossbar switching systems, notably N-5-3, SF-1, and the SE-2 PBX, in several locations including the Bramalea and Belleville regional laboratories. From 1968 to 1969 he acted as Northern Electric resident engineer in Athens, Greece, supervising the design modification and installation of switching systems. Eric became closely involved in electronic switching, and the SP-1 project in particular, on returning to the BNR central laboratories in Ottawa. His responsibilities have included call-processing in the toll switching version of SP-1, and development of the traffic operator position system. He is currently manager, SP-1 operator services design. Eric is a rapporteur within study group XI of the International Telegraph and Telephone Consultative Committee (CCITT) which is currently discussing stored-program controlled machines. He holds several patents in the field of crossbar switching.


In November, 1971, Intel invented and built the world's first single chip general purpose microprocessor, the 4-bit 4004. In April, 1972, Intel produced the new 8-bit 8008 microprocessor, which we used in the TOPS terminal position, a first for BNR/Northern.

January, 1974



electronic switching improves operator services


Eric Bierman

© 1974

Lower operating costs and more efficient operator deployment are the main advantages of introducing a new version of the SP-1 toll switching machine for operator-assisted calls. Known as TOPS, this system relieves the operator of many routine call-handling tasks.

The friendly operator, essential to the earliest telephone systems, is still one of a telephone operating company's greatest assets. While automatic switching machines have enabled these companies to respond to the staggering increase in demand for service, there are many types of calls that cannot be mechanically processed, and which demand an operator's help (see box below).

The majority of telephone calls in North America are made without the intervention of the operator, thanks to the direct distance dialing (DDD) system. These calls can be automatically routed through the network because every telephone has a unique 'address', made up of a three-digit area code followed by a seven-digit number. Billing information is obtained on most of these calls by automatic message accounting (AMA) equipment. The DDD system, in conjunction with AMA equipment, routes the call, notes the called number, and obtains and records the calling number through automatic number identification (ANI) equipment. The system also times the duration of the call and records it. Charges are computed from these details and included in the subscriber's monthly bill.

If the switching office handling the call is not equipped with ANI, an operator intervenes briefly to ask the caller for his number and to enter it into the AMA system. The call then proceeds as if ANI had been available.

This type of simple call requires little or no assistance from the operator. However, operator assistance is needed if the subscriber wishes to place a person-to-person or collect call, charge the call to his credit card or to a third telephone number, or make use of various other services. In most of North America the subscriber dials 0 for this assistance. The operator then controls the routing of the call, and the recording of timing and billing information. In a city the size of Montreal or Toronto, as many as 250 to 300 operators in five or six offices may be involved in call-processing at peak times.

In the last few years, the computer-controlled switching machine has been applied to take some of this burden from the operator's shoulders. For instance, a new addition to the Canadian-designed SP-1 family of computer- controlled switching offices is expected to reduce the average time an operator spends on a call by 25 to 45 percent, compared with the time required on a standard cord switchboard. Known as TOPS (traffic operator position system), it is expected to bring substantial savings to the telephone company through more efficient deployment of operators. Other savings are expected to accrue from reductions in maintenance costs, occupied space, and in ticketing (billing) errors.

Machines to help the operator

The need for such a machine became apparent in the North American telephone industry as direct-distance dialing (DDD) was introduced during the 1950's and 1960's. The DDD equipment took over the connection of simple calls, relieving the operator of much routine work, e.g. answering a request for connection, asking for the called number and the calling number, making the required connection by manually plugging in a cord to a switchboard jack, and actually dialing the number and recording call details.

Once in service, the automatic apparatus soon proved that it could help the telephone utility to increase efficiency, reduce errors, handle greater numbers of calls in a given time, and reduce customer waiting time. Telephone engineers then started to look at the feasibility of applying similar techniques to calls that were still being handled by the operator. These connections involved one, or both, of two factors — either the caller would not be billed directly, or he wanted to contact a particular person and needed the operator to verify that the person was available before starting to charge for the call. The procedures needed are quite complex. Figure 1 shows the steps involved in manually placing a person-to-person paid call on a cord switchboard. When the subscriber dials 0 his call is routed to the switchboard, which is divided into a number of positions, each served by an operator, A typical switchboard is shown in Figure 2. On each position rows of jacks and indicator lamps associated with incoming and outgoing lines are arranged vertically in front of the operator, and sets of extensible cords, a key set, and a mechanical timer, are placed on the horizontal surface, see Figure 3.

Manual SwitchboardTOPS
(trunk lamp lights)
operates talk key
plugs cord into trunk(call arrives) beep tone
talks to customertalks to customer
records calling number
records call type (person paid)keys call type (person paid)
records namenotes name
plugs into idle outgoing trunk
keys called number
asks for calling number
records calling number
(on answer)(on answer)
announces callannounces call
restores talk key
stamps ticketkeys start timing
stores ticket
(while handling other calls)
keys position disconnect
watches supervision
(on disconnect)
stamps ticket
pulls out cords
files ticket

Figure 1.
Operator Sequence for Person-Paid Call

line of operators

Figure 2.
The existing type of cord switchboard for handling operator-assisted calls.

operators position

Figure 3.
Each operator's position on the cord switchboard is provided with many sets of two extensible cords, which can be plugged into the incoming or outgoing jacks on the board in front of the operator, a keyset through which the operator enters numbers, and a mechanical timer which is used to record call duration

A lamp lights above one of the jacks to indicate that a call is waiting. The call also appears on other jacks every three positions along the board, so that several operators have the opportunity of answering. An operator answers by opening a 'talk key' associated with one of the cords on her position and inserting the cord plug into the jack. The light goes out, and she offers her assistance. Suppose the subscriber wants to place a person-to-person call to Mary Smith at 613-828-2761, the operator writes this name with a heavy black pencil on a computer mark-sense card — commonly referred to in the telephone business as a ticket — and marks the relevant spaces on it to record the called number, the time of day, the fact that it is a person-to-person call, and that the originator is to be charged for it. Meanwhile she takes an associated second cord and plugs it into the jack of an idle trunk circuit with access to the desired destination, indicated by another lamp. She enters the called number on the keyset, and the call progresses through the network automatically. While this is happening, the operator asks for the subscriber's number and records that on the ticket When the distant telephone is answered, she offers the call, and once Mary Smith is reached and the conversation begins, the operator removes her headset link from the connection by releasing the talk key and operates the timer to stamp the ticket with the time. The operator is now free to handle further calls with the other cords on her position. However, she must keep an eye on the two supervisory lamps associated with the cords which provide the first connection. When these lamps light, indicating that the parties have hung up, she must again stamp the ticket with the current time, put it in a bin for completed tickets, and take down the connection by pulling out the cords. All this may happen while she is handling another call, and watching the supervisory lamps of other connections. It is not unusual to find skilled operators with as many as five sets of cords connected.

The task is further complicated with coin-telephone calls because she has to look up the charges in a multileaf binder and ask for the correct coins to be deposited. Once that is done, she must start a timer to mark the beginning of the conversation. At the end of the initial period — usually three minutes — she re-enters the connection to notify the customer that his time is up and that if he wishes to continue the call he should pay an additional charge. When he finally hangs up she must re-ring him and ask him to deposit the overtime charge, which she has to calculate. The charge consists of the overtime rate per minute multiplied by the number of minutes, plus the applicable tax, all rounded to the nearest five cents.

Mechanization to help the customer

Research and development aimed at automating some at least of this process led eventually to the introduction of the traffic service position system (TSPS) No 1 by the Bell System in the United States. This machine, controlled by a special-purpose computer, is interposed between the local and toll offices. The position is a separate console equipped with keys, indicator lamps, and a digit readout panel. Through this console the operator can gain access to subscriber lines and to the network, and can enter calling information for billing purposes. She no longer has to plug in and disconnect cords instead, she presses buttons. Whereas on the cord switchboard operators had to actually search for the appearance of calls on the board, TSPS distributes them automatically. The subscriber is enabled to make operator-assisted calls by dialing 0 before the required phone number: this is known as a 0+ call. The call is automatically routed to TSPS, which records the called number, obtains the calling number through ANI, and stores it for billing purposes. Once the call is connected to whichever operator is free at the time, TSPS transmits the called number to the network.

Suppose the call is being made person-to-person, as just described. The operator depresses a 'PERSON PAID' key on the position and notes the name Mary Smith. When the conversation begins she merely pushes the 'START TIMING' key to tell the system to automatically note the time. Finally, she presses 'POSITION RELEASE' to remove her connection to the call and is immediately ready to receive another. Note that TSPS now possesses the called and calling numbers, the class of call (person-paid), and the time of start of conversation. It supervises the call automatically, until either customer hangs up. At that point the system notes the disconnect time, takes down the connection and sends the completed billing information to the AMA equipment.

On coin calls, the charge calculations are performed by the TSPS computer and presented to the operator via the readout panel. The operator is also relieved of the tasks of remembering to recall the subscriber after the initial three minutes is up. The system returns the call at the end of the three minutes to any operator who is free for the initial period report. Measurements show that the time spent by the TSPS operator on a call is reduced, on average, by 25 to 45 percent, compared with the cord switchboard. The simplification of the task reduces operator errors and makes training simpler.

In mid-1969, Bell Canada and Northern Electric approached BNR with the idea of designing a system similar to TSPS and based on the successful technology of the newly developed SP-1 family of stored-program controlled switching machines. In the Spring of 1970, some systems requirements were written for a system known as Operator Service Position System (OSPS). Similar to TSPS in concept and design, it would have used components of the SP 1 system.

Both TSPS and OSPS were large standalone systems, designed for offices with 100 to 300 traffic service operators. Work by the BNR systems engineering department in 1970 and 1971 showed that machines of this type would not be suitable for the Canadian or USA independent telephone company markets for a number of reasons. Most important, there were very few operator service systems of this size required. Besides, the total number of operator-assisted calls placed in North America was not increasing as rapidly as had been forecast in previous years, because the DDD equipment was assuming an unexpectedly large and increasing proportion of the total toll traffic. Both these factors made the proposed design look inappropriate for the available market. As a result of these investigations, the idea of a Canadian version of TSPS was firmly put to rest in the Spring of 1971

A new factor in the equation

A system better suited to Canadian needs was in fact evolved by BNR from the toll switching version of the SP-1, but starting with a different set of criteria. The catalytic factors were BNR's efforts to construct interfaces for the SP-1 with two types of existing operator positions. One of these, the CAMA unit (for centralized automatic message accounting) is employed in toll systems where not all of the subtending end offices are equipped with ANI, to enable the operator to note phone numbers for billing purposes. The other, the service analysis position, allows an experienced supervisor to make periodic checks on the quality of service provided in the toll office.

The CAMA unit consists of a desk, equipped with a headset which enables the operator to talk to the subscriber, and a multi-frequency (MF) tone key set on which she enters the calling subscriber's number for processing by AMA equipment. The SP-1 four-wire machine, as a modern stored-program control system, was provided with AMA recording on magnetic tape to receive ANI information from the local offices, but because many of these offices relied on operator number identification via the CAMA positions, the SP-1 also had to be provided with a CAMA interface.

It was set up through two trunk circuits, as shown in Figure 4a. An outgoing trunk, to which the subscriber's call could be routed, established a voice connection between subscriber and operator. An incoming trunk circuit was then added to provide a signaling path between the operator's key set and a receiver/sender, which was capable of receiving MF tones. This established one interface. The other — that with the service analysis position — was engineered in a rather different way. Most switching machines have a connection for this position, which presents an experienced operator — the analyst — with information about the progress of sample calls through the system. This information, including the number of the called subscriber, and the calling number keyed in by the operator, is displayed on a panel in front of her. By timing various steps in the process with a stopwatch, and comparing the displayed digits with the spoken requests, she can determine the efficiency and courtesy of the operators, and whether any delays or errors are the fault of the subscriber, the switching equipment, or the operator. The standard service analysis position was designed quite some time ago and as a result it employed some electromechanical signaling techniques which were no longer commonly used at that time. Rather than introduce these techniques in the SP-1 it was decided to alter the method by which service analysis was performed.

Consequently, BNR developed a system which transferred many of the timing and recording functions from the analyst to the switching machine, and designed a new type of console, with a cathode-ray tube for visual information display. The console was driven by the SP-1's existing teletypewriter link, which was already used to carry output messages for maintenance and administration purposes, and input commands from operating personnel. All timing information could now be displayed on the screen.

The task of noting call details was also given to the machine. Rather than have the analyst write the information on a card, the display system was made to enter a 'conversational' mode and prompt her to enter the required details on the keyboard. The system would then 'write' the complete service analysis record onto magnetic tape for later processing by a commercial computer service. Besides giving the SP-1 toll system a better service analysis position, this design also pointed the way to a simple and efficient operator-machine interface for traffic operator service units that would be suitable for the typical range of North American toll offices.

Cama position TOPS position

Figure 4 (a, b).
The design of the TOPS interface (b) on the SP-1 toll switching machine evolved from that of the CAMA position (a). The similarity of the two is apparent in this block diagram In (a) the operator's headset and the keyset are connected by separate two wire voice channels to the switching machine. The keyset link, which carries call signaling information, is routed to the central control complex via connections in the incoming trunk and the receiver/sender link network. However, this arrangement ties up an incoming trunk and a receiver/sender unnecessarily. The design adopted in (b) establishes the signaling link directly to the central control complex. The incoming trunk link becomes available for making the voice connection between the operator and the called subscriber.

A concept emerges

Towards the end of 1972 both the CAMA position interface and the service analysis position interface had been completed. The success of these exercises kindled fresh interest in an interface unit for a traffic operator service unit on the SP-1 toll switching machine. After some development, a simple demonstration of this service was held on the prototype switching machine in the BNR laboratories in November 1972. The arrangement adopted, depicted in Figure 4b, was very similar to the CAMA position interface, with modified incoming and outgoing trunk circuits, and used the existing teletypewriter system as in the service analysis interface. This demonstration, attended by representatives of Bell Canada and of the Northern Electric marketing group, showed that many of the manual tasks associated with operator-assisted calls could be efficiently taken over by a slightly modified SP-1.

Marketing exploration accompanied technical studies, and by the end of 1972 it was clear that a considerable demand existed for a small system of this kind. When the first potential sale was identified in January 1973 to RCA Alaska Communications Inc for their new toll office in Juneau, Alaska, TOPS advanced from a proven idea to a firm development project in BNR. Meanwhile, Bell Canada was still looking for a system that would match the need for two 250-position offices, for Montreal and Toronto. Further work showed that TOPS could satisfy both the initial Bell Canada requirements for a few large systems as well as the high demand for small ones.

The development of the equipment and associated computer programs has now reached the stage where the first TOPS consoles will be installed in the Juneau office in 1974. The toll SP-1 machine to which they are linked will handle incoming and outgoing DDD traffic and intertoll calls in addition to the operator-assisted calls routed by TOPS. Further TOPS installations will be made soon afterwards.

Table 1. SP-1 TOPS Features

  • full range of person-to-person collect and special call handling capability including coin and hotel originated calls.
  • automatic coin rating feature displays initial charge and interval to operators on call arrival
  • hot card list for trapping the ten most wanted fraudulent credit cards, in addition to the standard validity check performed automatically
  • broadcast message feature allows chief operator to send emergency messages to appear on the screens of all the operators
  • portable training controller plugs into any operator position to turn it into a training position
  • spare keys on keyboard, flexible screen formats on the display and stored program control of call processing logic will allow easy addition of future features as they arise.

With the development of TOPS, the SP-1 toll machine is equipped to handle the full range of operator-assisted calls, including person-to-person and collect calls, credit-card calls, and those made from hotels and coin phones. Other features are listed in Table 1. Most of the facilities needed to provide these services already exist in the SP-1 machine itself. Some new equipment must be added to this base unit, as indicated later, but the circuits involved are small, uncomplicated and inexpensive. With the exception of the operator's console, all additional units are located in the central office. Let us examine these units briefly (Figure 6).

System view

Figure 6.
Major functions of the SP-1 TOPS switching machine are outlined in this block schematic. The switching machine equipment itself, grouped in three major blocks — network, peripheral apparatus, and the central control complex — is located in the switching office, while the TOPS operator's console can be sited in any convenient location, near the office or remote from it. It is linked to the SP-1 by two four-wire voice channels. Its only other requirement is for 110-volt alternating current supply. Grey denotes new TOPS units.

The TOPS position, shown in Figure 5, was designed to maximise the operator's comfort and make for optimum performance. It consists basically of a console containing a video screen to display call information and a typewrite-style keyboard. The operator's headset, which enables her to talk to the subscribers, plugs in to a jack on the front of the console, and connects to the base unit through a separate four-wire voice channel. A substantial research and development program was undertaken by the BNR industrial design unit and human factors staff to arrive at the best console design. Studies of operators in the existing working environment were carried out in collaboration with Bell Canada, and supplemented by interviews. Some of the experiments, for instance, used full-scale mockups of the console and surrounding screens to explore people's preferences for privacy in their working conditions.


Figure 5.
Designed with the operator's comfort and efficiency in mind, the TOPS console has a video display, on which information appears during the processing of a call, and a typewriter-style keyboard, which the operator uses to enter the billing and timing information for processing by the machine. The keys are arranged in functionally related groups, with an abbreviated indication of the function on each. This view shows a prototype keyboard in the BNR laboratories.

In this small, relatively simple unit, the array of jacks and cords associated with the cord switchboard is replaced by electronic circuits. No longer does the operator have to manipulate the cords, keys and mechanical timer employed on the cord switchboard. Instead, she has only to operate keys, arranged in colour-coded functional groups within the keyboard. Screen and keyboard are linked to a position controller which sends standard teletypewriter characters to the base unit, via a data set, and receives standard characters back. A four-wire voice channel links the controller to the base unit. The position controller and data set are located within the console, together with a power supply which operates on standard 110 volt alternating current.

In the base unit, the most important additional hardware item is the position controller frame, which sends and receives teletypewriter characters to and from the positions. The interfacing of these items posed a timing problem to the BNR development group. The reason was that the base unit cannot 'know' when to expect a character from any position, and because characters arrive at a rate of 30 per second, the TOPS system must be ready to scan all the positions 40 times a second if it is to collect all the characters. As the system may support as many as 300 consoles, a disproportionate fraction of the time of the central processor could be occupied merely with scanning, if each position were scanned individually, The solution arrived at was similar to the matrix scanner designed earlier for the SP-1 toll switching machine itself. The individual position controller circuits are arranged in groups of 16. Only if a fresh character has arrived on a line within each group does the system examine each one individually. This arrangement reduces the scanning time by a factor of 16. The controller also contains a 64-character memory to act as an output buffer between the fast central processor, which can transmit one character every 10 microseconds, and the controller itself, which sends out one every 33 milliseconds. The position controller consists of just one printed circuit board. Each position controller frame, on which the boards are mounted, holds four shelves, each with 16 controllers.

Another new unit needed for the TOPS system is the position loop circuit, which provides the operator's voice connection to the calling and called subscribers through one incoming and one outgoing appearance on the trunk link network per operator loop. There are two loops for each position, each corresponding to a pair of cords on the cord switchboard. The operator is connected to one at a time. The position and loop circuit performs the switching of the operator's headset between the two loops, and the control of the connections from the headset through the network to the incoming and outgoing appearances of the loops in the switching machine.

The TOPS position and loop circuit is almost identical to the standard incoming and outgoing trunks on the SP-1 toll switching machine, and can be plugged in to the same location on the universal trunk frame. It employs the existing network connection, trunk selection, translation and outpulsing sequences.

Flexibility for new features

The inherent flexibility of stored-program control allows the many new features and types of service to be provided in TOPS with very little new or modified hardware, as we have seen. A number of new programs are required to handle the scanning and selection of positions, the information flow between operators and the base unit, automatic coin rating, the logic flow for a large number of different call types, and the additional automatic maintenance of new hardware units and software structures. Even so, the memory required for the TOPS generic program is only increased by 30 percent over that of the standard SP-1 toll switching machine. Figure 7 demonstrates how a call is processed by the TOPS system under the combined action of hardware and software. Through the TOPS approach to the provision of operator service, the operating company derives several benefits compared to the standard cord switchboard. The main one, as stated earlier, is the reduction in the average amount of time that an operator needs to handle a call. This is due to the simplification of the operator's task, apparent from Figure 1. Significant savings are expected to accrue to the operating company because of the more efficient manner in which operators can be deployed as a result. In addition, operator errors should be reduced. Manual operations such as the filling out of tickets are virtually eliminated. Billing information is recorded on magnetic tape. Besides being quicker, this recording method means less human involvement and therefore less chance of error.

Keyboard Keyboard Keyboard Keyboard Keyboard

Figure 7.

The progress of a 0+ non-coin call through the TOPS SP-1 machine is illustrated in this series of diagrams

(a)SP-1 identifies that the customer has dialed a 0, followed by the number that he wants to call. Digits dialed are received in a receiver/sender and stored in the memory of the central control.

(b) The operator is automatically alerted to the call by a beep tone in her headset, and a display on the console screen which indicates the class of service of the call — for example. 0+ non-coin. A connection is established through SP-1's switching network to enable her to speak to the calling subscriber.

(c) Immediately afterwards, a further connection is set up which allows the stored digits to be transmitted from a receiver/sender to the telephone network which extends the desired connections for the call. Meanwhile, the operator obtains details of the call from the subscriber.

(d) Now the called subscriber is on the line, and the operator verifies that it is the correct person and that they will accept the call. She still has the caller on the line also, so that she can talk to him if any problems arise.

(e) The operator has assured herself that the call has been set up satisfactorily, and now leaves the two subscribers connected. The video display on her console clears, leaving her free to handle the next call.

Thanks to the automatic diagnostic routines that are standard features of SP-1, maintenance costs for the equipment will be reduced by comparison with the cord switchboard. (This forecast is based on the proven performance of already installed SP-1 local offices). There is also a space saving, compared with other computer-controlled systems providing similar services, because TOPS does not require large amounts of additional hardware. Other systems need a complete switching machine to serve the traffic operator positions, interposed between the local and toll offices, Figure 8a. Moreover, in other systems each remote console needs its own switching apparatus which occupies a volume about equal to that of the console itself, and often all this apparatus has to be located in expensive rented premises. The TOPS consoles, on the other hand, are virtually self-contained, and need only a source of power, and two voice channels to connect them to the SP-1 base unit which is installed in the toll office, Figure 8b.


Figure 8 (a, b).
Low capital and maintenance costs are associated with the SP-1 TOPS, compared with other computer-controlled systems offering similar services. For these other systems, an additional switching unit is interposed between the local and toll offices (a). There are thus three separate entities involved, each used only partially for the service. By comparison, SP-1 TOPS makes use of the existing switching machine, and a console located at a convenient point, which may be many miles away if necessary.

Positions can be set up in small groups, or even singly in people's homes, as convenient. Thus TOPS consoles can be situated where operators are available, whether it is in the same building, the same town, or an unlimited distance away. No separate console is required for training new operators. Any position may be unplugged from the base unit and connected instead to a portable training module loaded with a tape cassette of pre-recorded training sessions. The system is designed so that no single fault can ever put more than one position out of action.

The inherent versatility gives each telephone company great freedom in designing and running a system. While one office may have few operator positions, the largest centres may need hundreds at busy times. The SP-1 TOPS allows each company to pick the exact number it requires for each location. Thus a small operating company or switching office can have this modern equipment at reasonable cost, and as its business expands can simply add further operator positions. The addition of new call features, as they arise in the future, may also be handled with ease. With the aid of the SP-1 TOPS, a telephone utility can plan to make the best use of the talents of its operators, make their jobs less routine and more rewarding, and also recoup some savings on its operating budget.