Manual / Guide · 1961
Technical Bulletin 961-473: Rotary Stepping Switches
Rotary stepping switch types, adjustment and application.
Manual / Guide · 1961
Rotary stepping switch types, adjustment and application.
TCI Library www.telephonecollectors.info ( Factory, development laboratories, and general office at Northlake, Illinois, U.S.A. AUTOMATIC ELECTRIC COMPANY is an organization of designing, engineering, and manufacturing specialists in the fields of communication, electrical control, and al1ied arts. For more than sixty years the company has been known throughout the world as the originator and parent manufacturer of the Strowger Automatic Telephone System. Today Strowger-type equipment serves over 75% of the world's automatic telephones. The same experience and technique that have grown out of the work of Automatic Electric engineers in the field of telephone communication are also being successfully applied on an ever-increasing scale to the solution of electrical control problems in business and industry. PRINCIPAL PRODUCTS Strowger Automatic Telephone Systems- Com· plete automatic central-office e quipment for exchange areas of any size, from small towns to the largest me tropolitan network s. Community Automatic Exchanges- Unattended automatic unit s for small rural or suburban area s, with faciliti es for sw itching into attended exchanges. Automatic Toll Boards - An adaptation of Strowger principles to toll switching, resulting in simplification of operators' equipment and greater economy of operating and toll-circuit time. Private Automatic Exchanges - Available in various capacities, with or without central-office ( connections, and with facilities for special control services to meet the needs of the user. P.B.X. Switchboards- A complete range of cordless and cord types for the modern bu siness. Telephone Instruments - Modern des igns for automatic or manual exchanges, including the Monophone- the world's most attractive and e fficient hand se t telephone. Exchange Accessory Equipment - Auxiliary exchange and sub station eq uipment, including manual de sk s, te s ting apparatus, tran sm i ss ion eq uipment, and all accessorie s needed for the operation and mainte nance of the modern telephon e exchange. Makers also of electrical control apparatus for industrial, engineering, and public utility companies, telephone apparatus for railroads and pipe-line companies, private telephone systems of all types, electrical and communication devices for aircraft and airways control, and special communication apparatus for military and naval departments. Copyright © 1961 Automatic Electric Company TCI Library www.telephonecollectors.info ( CONTENTS Page 1. 1.1 1.2 1.3 2. 3. 4. 5. 6. 1 GENERAL Rotary Stepping Switches Rotary Stepping Switch Classification Use of Rotary Stepping Switches . 1 1 1 MECHANICAL COMPONENTS AND OPERATION 3 2 .1 2 .2 2.3 2.4 3 3 3 4 The Bank Assembly . Wiper Assembly The Driving Mechanism • Off-normal and Interrupter Springs ELECTRICAL CHARACTERISTICS 5 3 .1 3 .2 3 .3 3.4 3.5 3.6 3. 7 5 5 5 5 7 7 7 Coils Insulation Breakdown Current-carrying Capacity . . Contact Protection (Spark Suppression) Precious Metal Contacts • A-c Operation Rotary Stepping Switch Pulse Range ELECTRICAL STEPPING CONTROL AND OPERATION 8 4.1 4.2 4.3 4.4 4.5 4.6 4. 7 4.8 9 10 11 12 13 14 14 15 Typical Control Circuit - Minor Switch (Figure 12) . . Typical Control Circuit - Rotary Stepping Switch (Figure 13). OCS Relay Remote Control Automatic Hunting - Selecting a Circuit . • Control of Consecutive Operation of Separate Circuits (Figure 19). Timed Pulses (Figure 20) . . Return to Normal Position (Homing) Pulse Inversion (Figure 24) OPERATING CONDITIONS AND PREVENTIVE MAINTENANCE 15 5 .1 5 .2 5 .3 5 .4 5 .5 15 16 16 18 18 General Operating Considerations • Preventive Maintenance Rotary Stepping Switch Cleaning Adjustment . Lubrication . MINOR SWITCH • 19 6.1 6 .2 6.3 6 .4 6 .5 19 19 20 20 20 General Description • Coil Information Main Assemblies Mounting Preventive Maintenance • TCI Library www.telephonecollectors.info CONTENTS (Cont'd.) Page 7. 8. 9. 10. 11. SERIES OCS RELAY • 24 7 .1 7 .2 7 .3 7 .4 24 25 27 27 General Description . Main Assemblies Mounting Preventive Maintenance TYPE 13 (25-Point) AND TYPE 14 (50-Point) ROTARY SWITCHES 30 8 .1 8 .2 8 .3 8.4 General Description (Figure 33) Main Assemblies Mounting Preventive Maintenance 30 30 32 32 TYPE 26 ROTARY STEPPING SWITCH 36 9.1 9.2 9.3 9.4 36 37 37 38 General Description . Main Assemblies Mounting Preventive Maintenance TYPE 40 AND TYPE 44 ROTARY SWITCHES 40 10.1 General Description . 10.2 Main Assemblies • • • • 10.3 Arrangement for 20- or 30-Point Operation (Type 40) and 22- or 33-Point Operation (Type 44) 10.4 Mounting 10.5 Preventive Maintenance 40 41 TYPE 45 ROTARY SWITCH 48 11.1 11.2 11.3 11 .4 11.5 11.6 48 48 49 49 50 50 General Description Main Assemblies 50- Point Operation Mounting A-c Operation Preventive Maintenance TCI Library www.telephonecollectors.info 42 42 42 ( ( TCI Library www.telephonecollectors.info ( ' '--' - - I . ( Rotary stepping switches. TCI Library www.telephonecollectors.info ROTARY STEPPING 1. GENERAL Connections in some automat~c telephone systems and many industrial control functions are accomplished by small, high-speed rotary stepping switches acting in response to electrical control pulses. These rugged devices require only minor adjustment and maintenance in the field. 1.1 Rotary Stepping Switches Rotary stepping switches (frontispiece) are sturdily constructed selecting mechanisms consisting of the following: SWITCHES contact; and when the selected circuit is no longer needed, the switch is reset by operation of a release magnet which returns the wipers to the normal position along a path which is opposite to the direction in which the switch was stepped. 1.3 Use of Rotary Stepping Switches 1.3 .1 Telephone system use. Rotary stepping switches are used in automatic telephone systems in the following ways: a. As linefinders. a. A driving mechanism. b. A number of pairs of wipers fixed to a rotating shaft. c. Bank levels (equal in number to pairs of wipers), all assembled to a frame. (A bank level is an arc of contacts separated from each other by an insulating material.) When a pulse is fed to the switch, the driving mechanism rotates the shaft and wipers around the bank contacts - one step per pulse. When the wipers are resting on a bank contact, a circuit is completed through each pair of wipers and the associated bank contact to perform the control function desired. Though not true rotary stepping switches, type OCS relays are also covered in this bulletin. OCS relays use a rotary switch driving mechanism to rotate a number of cam discs. Armature spring fingers ride the crest of the cams and open and/or close a fixed number of relay spring pile-ups to control secondary circuits as the cams rotate. b. As connectors. c. As allotter switches. d. For trunk distribution. e. For ring-code selector. f. For dialed number registration. g. For sequence control. 1.3 .2 Industrial use. In industrial signaling and control, rotary stepping switches are used in increasingly greater numbers for applications requiring selection, distribution, totalizing, and counting. Typical applications include: a. Counting and routing of materials on conveyors. b. Sequence control of machine tool operations. 1.2 Rotary Stepping Switch Classification c. Remote control of substations. Rotary stepping switches are classed either as unidirectional or around-and-return switches. Unidirectional switches step in one direction only. Wipers are so arranged that when all bank contacts have been traversed, the switch is in its reset or "normal" position. Such a switch must be stepped to its normal position after each use. Around-and-return switches step in one direction to the selected d. Control of radio transmitters and monitoring of programs. e. Control of airport lighting and radio beacons. f. Remote control of aircraft signaling systems. 1 TCI Library www.telephonecollectors.info /INDICATOR WHEEL / C NONBRIDGING WIPER <!) / O F F - NORMAL CAM LOBE ( ...--WIPER ASSEMBLY INTERRUPTER SPRINGS WIPER SHAFT STOPPING TEETH DRIVING SPRING-__::~~:--" DETENT STOP PAWL SPRING-~~~--1 PAWL SPRING OFF-NORMAL SPRINGS ( Figure 1. Typical rotary switch components. TERMINAL 1 ( BANK CONTACT Figure 2. Typical molded bank levels. 2 TCI Library www.telephonecollectors.info g. Remote control of motor speeds by varying field resistance. h. Remote control of current supply equipment for arc welding. i. Automatic control of tear gas release in burglar protection systems. 2. MECHANICAL COMPONENTS AND OPERATION A rotary stepping switch consists of three main assemblies mounted on a metal frame. These assemblies, illustrated in figure 1, are the bank assembly, the wiper assembly, and the driving mechanism. 2 .1.3 Wiper brush springs. There are two types of functionally identical wiper brush springs in use. One type is made of a single thickness of contact material with the brush end split, and the other end forming a terminal. The split tips are bent apart and tensioned. The other type of brush spring is made of two thicknesses of contact material. At the brush tip end, the two thicknesses of contact material are bent apart and tensioned; at the other end, the two thicknesses of material are pressed together forming a terminal. When the switch is assembled, these bent tips make electrical contact at all times with the associated wipers of that level. 2 .2 Wiper Assembly 2.2.1 Components. 2 .1 The Bank Assembly The wiper assembly consists of a ratchet and hub assembly, a wiper blade for each bank level, and an indicator and off-normal cam. 2.1.l Laminated levels. The bank assembly is built up from the appropriate number of bank levels. A bank level may appear in either of two functionally identical forms. The older, laminated level is assembled of a layer of insulating material, a layer of contacts, and another layer of insulating material. This form will continue to be used on the minor switch, and type 13, 14, and 26 rotary switches. The newer, molded level (figure 2) is produced by inserting the contacts into a mold and, under heat and pressure, forcing plastic molding compound between and around the contacts. This form will appear on the type 40, 44, and 45 rotary stepping switches and on any new type switch which may be introduced. Each bank level consists of insulating material, contacts, and wiper brush springs. 2 .1.2 Molded levels. The insulating material is either phenolic plastic laminate or polyester sheet, used in the assembled levels, or glass fiber filled Diallyl Phthalate (DAP) plastic molding com pound used in the molded levels. Normally, the contacts are made of phosphor bronze, but for special applications where contact resistance is critical, silver-inlaid or gold-plated contacts can be built into a level at the customer's option. Gold-plated contacts may be used in almost any environment; silver-inlaid contacts may be used only in controlled environments because of silver's readiness to oxidize and because of the poor conductivity of silver oxide. The components of the wiper assembly are permanently assembled. Each wiper blade is made up of two phosphor-bronze springs. The ends of the wiper springs are bent into wiper tips which make electrical contact with both sides of a bank terminal. Wipers are designed so that when one pair of tips is in contact with the bank, the other(s) is not in contact. 2.2.2 Wiper tips. There are two kinds of wiper tips: bridging and nonbridging, both of which are often supplied on the same wiper assembly. a. Bridging wipers have long flat tips (figure 1) which, during rotation, permit the wiper to engage the next bank contact before breaking away from the previous contact. Bridging wipers are used when the circuit through them must be continuous and unbroken. b. Nonbridging wiper tips (figure 1), during rotation, leave one bank contact before engaging the next, avoiding electrical interconnection between circuits of adjoining bank contacts. 2 .3 The Driving Mechanism There are two types of driving mechanisms: indirect and direct. The indirect-drive mechanism is "cocked" when the motor magnet is energized, and steps when the motor magnet is de-energized. The direct-driving mechanism steps when the magnet is energized. This type of driving mechanism is peculiar to the minor switch. 3 TCI Library www.telephonecollectors.info 2.3.2 Direct drive. rARMATURE MOTOR MAGNET RATCHET STOP SPRING Figure 3. Indirect-drive mechanism. 2.3.1 Indirect drive. The indirect-drive mechanism (see figure 3) consists of a motor magnet and armature, a drive pawl, a drive spring, a detent stop spring, and armature stopping teeth. When the motor magnet is energized, the armature is attracted to the magnet, compressing the drive spring, setting the pawl into the next ratchet tooth, and disengaging the stopping teeth from the ratchet (figure 5). When the motor magnet is de-energized, the drive spring acts on the armature causing the pawl to rotate the ratchet and wipers. When the pawl has completed its travel, the stopping teeth engage the ratchet teeth to prevent overthrow (excessive advance of the wipers). The direct-drive mechanism (figure 4) consists of a rotary magnet and armature, a drive pawl, and a rotary armature restoring spring. When the rotary magnet is energized, the armature is attracted to the magnet core. The armature motion pushes the pawl into the ratchet teeth, rotating the ratchet and wipers one step. When the rotary magnet is de-energized, the pawl is returned to its original position by the action of the rotary armature restoring spring. The direct-drive mechanism is released by an associated release mechanism consisting of a release magnet and armature, a ratchet dog, a release-armature restoring spring, and a wiper assembly restoring spring. When the release magnet is energized, the armature is attracted to the magnet and the ratchet dog is removed from the ratchet. The wipers are reset to their normal position by the wiper assembly restoring spring. When the release magnet is de-energized, the ratchet dog is again engaged into the ratchet teeth by action of the releasearmature restoring spring. 2 .4 Off-normal and Interrupter Springs 2.4.1 Off-normal springs (figure 1). Off-normal springs are used to control or operate auxiliary circuits and with the interrupter springs can be used to home the switch to its normal position. When the wipers are stepped from their normal or home position, RELEASE ARMATURE RELEASE MAGNET ROTARY MAGNET 0 ROTARY ARMATURE RELEASE ARMATURE @ -~-~RESTORING SPRING - - I "---RATCHET DOG PAWL--RATCHET (PART OF WIPER - - ASSEMBLY) I ,...__BANK ASSEMBLY / / WIPER ASSEMBLY RESTORING SPRING Figure 4. Direct-drive mechanism. 4 TCI Library www.telephonecollectors.info Figure 5. Pawl arul stopping teeth action. the off-normal springs operate, and restore when the wipers return to their home position. 2.4.2 Interrupter springs. Interrupter springs are used to control an auxiliary circuit or to provide a self-interrupting operate circuit for the motor magnet. Interrupter springs are operated when the armature is moved toward the magnet. 3. ELECTRICAL CHARACTERISTICS The electrical operating components of rotary switches are the motor (or rotary) magnet, the interrupter and off-normal springs, the wipers, the brush springs, and (in the case of the minor switch) the release magnet. Their mechanical operation and physical description are discussed in section 2. 3 .1 Coils Magnet coils, operating at the voltage for which they were designed, will stand continuous pulsing indefinitely. Coils can be supplied for special conditions such as high humidity, or prolonged, continuous operation. When coils are to be held energized for long periods of time, a limiting resistance should be inserted in series with the coil (see figure 6), after the switch is operated. An extra pair of break (form B) interrupter springs can be used to perform this function. I S PARK SUPPRESSOR HOME INT. SPGS. OFF - NORMAL SPGS. Figure 6. Limiting holding current of motor magnet. 3 .2-lnsulation Breakdown Bank and wiper assemblies on the type 44 and type 45 rotary switches are tested to withstand an a-c insulation breakdown test at 1250 rms. Insulation can be supplied which will withstand breakdown at higher voltages. 3 .3 Current-carrying Capacity A wiper, resting on a bank contact, can safely carry 3 amperes, a.c. or d.c. A circuit should be opened before stepping the wiper away from the bank contact. When this cannot be done, limit the load to be broken to 11.5 watts (O.l ampere at 110 volts) to prolong wiper and bank contact life. 3 .4 Contact Protection (Spark Suppression) Contact ratings (section 3.3) are based on the use of adequate spark suppression equipment. If spark suppression is not provided, contact life will be reduced. Usually adequate spark suppression is obtained by connecting a series capacitor and resistor in parallel with the (operating) contacts. The resistor-capacitor values listed in TABLE I are for use with standard coils for the switch type shown. 3 .4.1 Noninductive resistors. For alternating current, a noninductive resistor alone may be effective if slight current loss is allowed. Under certain conditions, a noninductive resistor of high value connected across the load terminals is often effective. For improvement, use this method with those described above. 3 .4.2 Silicon carbide varistors. Silicon carbide varistors (figure 7) are available for use as spark suppressors with type 44 and type 45 rotary switches and with the OCS relay. The resistance of a varistor varies approximately as the square of the applied voltage. When voltage is applied to the magnetcoil circuit, the varistor draws very little current; when the magnet - co i 1 circuit is opened, the varistor offers a low-resistance path to short circuit the high-voltage surge caused by the collapse of the magnetic field. 5 TCI Library www.telephonecollectors.info TABLE I. COILS AND CONTACT PROTECTION Type 13 (25 point), Type 14 (50 point), and Type 26 (11 point) Rotary Switches. Operate Volts d.c. Coil Resistance Ohms Capacitor 6 12 24 48 60 110 4.4 9.4 30 100 190 650 0.5 0.5 1.0 1.0 1.0 0.2 µf Noninductive Resistor Ohms Varistor 10 10 125 200 200 200 Type 40 (10 point), Type 44 (11 point) Rotary Switches, and OCS Relay. Operate Volts d.c. Coil Resistance Ohms Capacitor 6 12 24 1.9 7 30 2.0 0.5 0.4 µf Noninductive Resistor Ohms Varistor 3 10 75 RY-56 100 RY-57 150 150 500 RY-57 RY-57 RY-58 Noninductive Resistor Ohms Varistor 3-level Switch 48 140 0.2 6- level Switch 48 60 110 120 155 650 0.2 0.2 0.03 Type 45 (26 point) Rotary Switch. Operate Volts d.c. Coil Resistance Ohms Capacitor 6 12 24 48 60 110 1.7 5 9.4 30 100 190 650 3.0 2.0 0.2 0.2 0.1 0.03 µf NOTE: See TABLE IV for Minor Switch Coil Data. 6 TCI Library www.telephonecollectors.info 2.5 10 50 200 200 200 RY-56 RY-57 RY-57 RY-58 readiness to oxidize (tarnish). Silver inlay does not alter the maximum carrying capacity of the switch contacts. 3 .6 A-c Operation ( The type 40, type 44, and type 45 rotary switches and the OCS relay may be used with 115 volt, 60 cycle alternating current by using a suitable rectifier unit (figure 8). Control switching must be done on the d-c side of the rectifier only. Figure 7. Silicon carbide varistor. 3 .4.3 Resistor-capacitors. 3. 7 Rotary Stepping Switch Pulse Range Switches are normally factory adjusted (speeded) for use with a resistor-capacitor spark suppressor. When a switch is ordered to be furnished with a varistor, the switch will be adjusted for the varistor. If any other method of spark suppression is to be used, the switch will have to be readjusted in the field for proper operation. Current pulses, from a pulsing relay to a switch motor magnet, may be established by the operation of a standard telephone dial. These interruptions in the circuit of the pulsing relay, at the impulse springs of the 3 .5 Precious Metal Contacts ( - 100 - -1- 90 The standard phosphor-bronze bank contacts and wipers have sufficient contact wipe and pressure to insure reliability when switching circuits of normal control power levels. They are not suitable for use in circuits where contact resistance is critical. For thermocouple or strain-gage switching or in a circuit where measurements at low power are being made, gold-plated contacts must be used for satisfactory results. Gold plating does not alter the maximum carrying capacity of the switch contacts and may be used under almost any conditions of ambient atmosphere. -- I'- - ~ - 70 l&J ~ TYPE 45 ROTARY SWITCH 60 :Ii' \ l&J )~ ~ l&J / 40 ,, / ........... 30 v ,,~ ./ 20 ~"' ~v + 40MF. 150V I./' 1- z 50 10 v v v - .- \ 4 RECT. + r-- 80 Cl. Silver-inlaid bank contacts and silver-plated wipers may be used when low-contact resistance and low microphonic noise level are required. These contacts should be used only in controlled atmospheres because of silver's --- -- -- ~ // ./ ' v / ~ \ TYPE 40, 44 ROTARY SWITCH AND OCS RELAY 'l / TERM. BLK . ·~~~ ( REMOTE CONTACT S G: G o~ 5 10 15 25 30 35 PULSES PER SECOND CLOSE TO STEP w 2 FOR TYPE 40, FOR TYPE 44 ROT. TYPE 45 SW. AND OCS ROT. SW. RELAY 0 CLOSE FOR SELFINTERRUPTE D OPERATION Figure 8. A-c rectifier - schematic diagram. Figure 9. oPerating range - type 40 and type 44 rotary switch and OCS relay. dial, consist of a closed circuit period and an open circuit period referred to as "percent make" and "percent break" respectively. The length of the closed circuit period or the open circuit period is a percent of the length of the 7 TCI Library www.telephonecollectors.info entire pulse period. A comparison of speedpulse ratio curves between four-level, type 44 and type 45 rotary switches at 48 volts is shown in figure 9. These curves show that the percent make of the entire pulse period required for switch magnet operation increases as pulsing speeds increase. That is, the percent make required for switch magnet operation becomes larger; until at 35 pulses-per-second, the maximum pulse limit for the switch has been reached. The curve, located in the upper portion of the graph, indicates the greatest length of pulse (at various speeds) that will allow sufficient time for the magnet to properly restore. The complement of any value on this upper curve is the shortest percent break required for satisfactory switch magnet release. The upper and lower curves, therefore, define the limiting conditions between which a pulse to the switch magnet may vary. At 10 pulsesper-second, the lower curve shows that the shortest pulse that will operate the switch magnet is approximately 18 percent make for the type 45 switch (.018 seconds, operate time); and the longest pulse that will give satisfactory operation is 95 percent make (.095 seconds) or 5 percent break (.005 seconds, release time). In this case, the percentmake values and time values in milliseconds are the same, because there are 100 milliseconds for each impulse (10 pulses-persecond). At 15 pulses-per-second, the total time for an impulse period is .067 seconds; and referring to the lower curve, this equals 26.5 percent make required for operation which, by proportion, gives .018 seconds minimum operate time. Switch magnet operate time (in seconds) changes but little with changes in impulse speed for a given voltage. Longer operate times, that is a longer pulse (higher percent make), are necessary for low voltages because of the slower rate at which the current builds up in the switch-magnet coil. 4. ELECTRICAL STEPPING CONTROL AND OPERATION The operation of rotary stepping switches may be either manually controlled, or controlled by an automatic self-interrupted circuit. For automatic operation, the interrupter springs are connected into the operating circuit and the switch acts as a non-numerical or s e 1 f - c y c 1 in g device. It will automatically search its bank contacts for a special circuit condition such as the presence-of-ground or battery, the absence-of-ground, etc. For manually controlled operation, pulses may be transmitted to the switch magnet coil from a dial, push button, or other remote control device. Two typical circuit arrangements for the operation and remote control of equipment are shown in figures 12 and 13. 100 ....._ ~ :-.:::: ~- 90 .... ~- r-.. ~ .... } 80 I I TYPE 13 ,. 70 , _, I I , 1/ , ,/ • v / 26 J ' TYPE ,' , / "r:/ 30 ", , ...l' ,J 20 10 ,/ u 40 v ,V SPEED - PULSE RATIO CURVES - - - TYPE 13 ROTARY SWITCH-4 LEVELS - ---TYPE 26 ROTARY SWITCH - 4 LEVELS_ I Figure 10 shows pulse-ratio curves which define the limiting conditions for the type 13 (25 point) and type 26 (11 point) rotary stepping switches. Figure 11 contains the pulse-ratio curves for the minor switch. ·- __ ""'-- -- -- 1~ 10 I I I I I I 15 20 25 PULSES PER SECOND I 30 I I 35 Figure 10. ()perating range - type 13 and type 26 rotary switch. 8 TCI Library www.telephonecollectors.info 100 ~ 90 held operated.) The operation of relay A closes ground from the back contacts of relay B through make springs of relay A, and the normally closed off-normal springs of the minor switch to battery through the relay C coil. Relay C operates to prepare a pulsing path to the rotary (ROT.) magnet. ,........._ ;-...... ;-...... r:::::: ~ F "-... r-.... ro-:: ~ ~ ~r-........ r-e-.. ... 80 ................... ~ -/.. -- I .... , '-, -, J ~ 60 v ......... )(' I <( :::!: I- ~ 50 J u 0:: w / / E I Q. J 40 ./ J 30 J / , .......... / / / ,/ / v / }"' I vv / 20 A-8: 48 VOLT SWITCH 10 Y::: - C-D: 24 VOLT SWITCH, I MF., 200 OHMS ';" E-F: 12 VOLT SWITCH, 1/2 MF., 10 OHMS 5 10 The desired digit is dialed. The first opening of the dial springs, as the dial restores, causes relay A to release and close ground from the back contacts of relays B and A through the make springs of relay C to the secondary winding of relay C. Ground is also closed to the ROT. magnet of the minor switch. The energization of the ROT. magnet steps the wiper assembly to the first set of bank contacts. The forward movement of the wiper assembly opens one pair and closes the o1her pair of off-normal springs. Opening the normally closed pair of off-normal springs opens the operating circuit for relay C. However, relay C is held operated through its make springs in parallel with the ROT. magnet. / v / y / I / ~ / ,/ / I / J ............ 70 15 I I 20 25 - The closing of the dial impulse springs, at the end of the first pulse, will reoperate relay A to remove ground from the holding winding for relay C and the rotary magnet. The rotary magnet is de-energized and therefore releases, but the slow-releasing characteristics of relay C cause it to remain momentarily in the operated position. I 30 35 PULSES PER SECOND Figure 11. oPerating range - minor switch. 4.1 4.1.1 Typical Control Circuit (Figure 12) The second opening of the dial impulse springs, for the second pulse, again releases relay A to close ground to the holding circuit for relay C and to the rotary magnet. Relay C remains operated during the interval between successive dial pulses, and the rotary magnet is reenergized to step the wipers ahead one step. Minor Switch Stepping the switch. Operation of a nonlocking DIAL key closes the circuit for relay A. (The DIAL key must be A B c MINOR SWITCH DIAL OFFNORMAL SPGS. TOP c0 0 0 DIAL KEY (NONLOCKING) ROT. ~I• RLS. KEY (NONLOCKING) Figure 12. Typical remote control circuit - minor switch. 9 TCI Library www.telephonecollectors.info NOTE: The control methods used for rotary stepping switches in general are not applicable to the minor switch. The dial comes to rest at the completion of the series of pulses corresponding to the digit dialed. Relay A reoperates but relay C, after the expiration of its slow-release interval, releases. Release of the DIAL key restores relay A. 4.1.2 External control circuit selection. A control relay has been connected to the third contact of the bottom level of bank contacts (see figure 12). When relay C releases, at the end of the three pulses for digit three, the wipers are resting on the third set of bank contacts. Ground, through the back contacts of relay B, relay C, and the common bank contact C, is closed to the control relay via the wiper. The control relay operates and locks to an external ground at its own contacts. Operation of the control relay in turn performs the required control function. In a similar manner, a control relay may be connected to each bank contact. By dialing different digits, various relays are energized to perform separate control operations. 4.1.3 Circuit release. Momentary operation of the RLS key (see figure 12) closes ground to relay B. The operation of relay B closes ground to the RLS magnet of the minor switch via the make contacts of relay B and the make pair of offnormal springs. This causes the operation of the RLS magnet which restores the wipers to normal. The operation of relay B also removes ground from the lower or BOTTOM bank preventing false operation of any control relays while the wipers are restoring. The off-normal springs reoperate opening the release magnet and the relay B locking circuits. A c 4.1.4 External control circuit release. Digit "O" is dialed to discontinue the external control function (see figure 12). This time the wipers will stop on the 10th bank contact, which is wired to the secondary winding of the control relay. Relay C, upon restoring, grounds this lead setting up a magnetic field which opposes that in the primary winding of the control relay. The cont r o 1 relay restores. When the RLS key is operated, the circuit is restored to normal. 4.1.5 Safety feature. The nonlocking DIAL key or push button makes it impossible to operate this circuit except when manually holding the key in its operated position. The key automatically restores when the operator removes his hand. This arrange ment prevents false operation of equipment by an accidental or unauthorized manipulation of the dial. The DIAL key may be concealed to further reduce the possibility of false operation. 4.2 Typical Control Circuit - Rotary Stepping Switch (Figure 13) 4.2.l Stepping the switch. Operation of the DIAL key operates relay A which, in turn, closes ground to operate relay B. The desired digit is dialed. Relay A releases on the first opening of the dial springs, as the dial is restoring. With relay A normal, ground is closed via make contacts of relay B to slowreleasing relay C and the motor magnet MM. Both relay C and the motor magnet operate. At the end of the first pulse, the dial springs close and relay A reoperates. Ground is removed from the motor magnet MM and relay C and is returned to the winding of relay B. The slow-release characteristics of relays B and C cause them to remain operated during the restoration of the dial. Relay B will remain B DIAL BRIDGING •l't-#N-7 DIAL KEY (NONLOCKING) Figure 13. Typical remote control circuit - rotary stepping switch. 10 TCI Library www.telephonecollectors.info operated while relay A is normal; and relay C will remain operated while relay A is operated. The motor magnet MM, however, de-energizes with each reoperation of relay A and steps the wiper assembly one step until the dial has restored. 4.2.2 External control circuit selection. The dial restores after a series of pulses, and relays A and B remain operated. Relay C, at the expiration of its slow-release interval, restores closing ground via the wiper brush contact to the particular control relay connected to the bank terminal on which the wipers rest. This control relay operates and locks to an external ground through its make contacts. 4.2.3 Circuit release. The restoration of the DIAL key releases relay A which releases relay B, and ground is closed via the normally closed contacts of relays A and B, strapped level A bank contacts over two paths: via the now closed contacts of relay B to operate relay C, and via the interrupter springs to operate motor magnet MM. Energizing motor magnet MM operates the armature of the switch which opens the interrupter springs and de-energizes motor magnet MM, etc. This alternate operating and releasing of the switch under control of its interrupter springs, steps the wiper assembly to the home or normal-bank terminal. At this point, the strapping of the level A bank terminals is discontinued, and the operating circuit for the motor magnet MM is opened. The switch remains on the home bank contacts. Relay C is held operated by the ground supplied through the strapped bank contacts and associated wiper until the switch has reached its home position. Relay C then releases. Relay C, when operated, removes ground from the wiper of level B (nonbridging) to prevent false operation of other control relays as the wipers sweep over bank contacts. The operated control relay is held operated by an external ground through its make contacts. Bridging wipers maintain the operating ground for motor magnet MM and relay C, between bank contacts, while the switch is being stepped to normal. OCS relay. In the relay, a cam replaces the wiper assembly and spring assemblies replace the bank contacts. Pulsing the rotary magnet rotates the cams, which are divided into cut and uncut portions, thus closing and opening spring assemblies to control external circuits. As a remote controlled switch, the relay circuit arrangement usually includes secondary controls for homing, step absorption, or both. Step absorption is necessary to reduce the 36-step cycle to the number required. 4.3.1 Remote control with homing. Figure 14 shows the basic operate and homing controls. Cam No. 1 is usually used for homing control and has a one-step cut. Its springs, referred to as off-normal springs, open in the home position. Pulses, via the operate lead, step the cam assembly. Cam No. 1 closes its springs, after the first step, and prepares the homing control to the motor magnet. Other cams pulse their springs according to the divisions of cut and uncut portions. When the homing switch is closed, the motor magnet will step the cams self-interruptedly to the home position. Cam No. 1 opens the off-normal springs. The one homing notch in cam No. 1 assumes that the OCS relay makes the 36-step revolution for each useful work cycle of the controlled device. If the controlled device does its task in 18 or less steps, the OCS relay cam can be cut to control two or more work cycles for each revolution. In this case, separate homing notches (if required) can be provided for each work cycle. SPARK SUPPRESSOR OPERATE ·I~ HOMING ' -......,.,__ _ OFFNORMAL SPGS. __ INT. SPGS. ·I~ -->-------' CAM I 4 .2 .4 External control circuit release. The digit • 'O'' is dialed to release the external control circuit. This is similar to the arrangement described in the preceding section 4.1.4. CAM 2 4 .3 OCS Relay Remote Control The basic methods for controlling rotary stepping switches, by remote pulses and automatically by self-interruption, also apply to the Figure 14. Remote control cmd homing circuit - OCS relay. 11 TCI Library www.telephonecollectors.info SWITCH 4 .3 .2 Remote control with step absorption and homing. Step absorption reduces the 36-step cycle of the standard relay to any number required for one work cycle. Its operation is similar to that of homing control except that the cams recycle each time through a definite predetermined number of steps. Cam No. 1, depending upon the number of steps to be absorbed, may have more than a one-step cut. For recycling, in general, a homing control is usually used with the step-absorption circuit. Figure 15 illustrates a typical circuit arrangement. Assuming a work cycle of 33 steps, cam No. 1 is cut for three steps. The remaining cams are designed, as required, to operate their cam springs for only 33 steps. A OPERATE 8 2 0 CAM I /~ \ 1 I ~ SWITCH I OTHER CAMS AS REQUIRED Figure 16. OCS relay replacing two coil latch relays. SPARK SUPPRESSOR ..rWJv-j11 4.3 .3 Remote control with replacement for a two-coil latch relay. INT. SPGS. Figure 15. Typical control circuit wUh both homing and step absorption. The homing control has been prepared by cam No. 1 for 33 steps. At step 33, operate pulsing ceases and cam No. 1 drops to close the stepabsorbing ground to the motor magnet. The cam assembly is automatically stepped three times and three steps are absorbed. Having reached the home position, cam No. 1 raises and removes the step-absorbing ground from the motor magnet; and the relay comes to rest at its normal position. Closing the homing switch operates relay B. Relay B locks to ground at its contacts, operates relay A, and causes the motor magnet MM to step self-interruptedly. Relay A locks to ground at the homing switch. The motor magnet MM steps the cams to position 33 where relay B releases. However, cam No. 1 continues to operate motor magnet MM for three more steps. In position 36, cam No. 1 opens the motor magnet circuit. When the homing switch is opened, relay A releases. The OCS relay is sometimes used to replace a two-coil latch relay operated over two separate leads. The control circuit shown in figure 16 illustrates this arrangement. All cams are notched on every other step. The operation of switch 1 closes a circuit through the springs of cam No. 1 and the interrupter springs to the motor magnet MM. The relay takes one step, self-interruptedly, and changes the position of all cam springs. The circuit is now prepared for switch 2. Further closures of switch 1 will have no effect on the relay until switch 2 has been operated to restore the relay to normal. 4.4 Automatic Hunting - Selecting a Circuit 4.4.1 Absence-of-ground searching (figure 1 7). The arrangement shown in figure 17 searches for an absence-of-ground. A startgroundfrom a control relay's contacts or from a key (via the normal contact, the wipers, and the rotary switch interrupter springs) energizes the motor magnet MM. The motor magnet armature opens the interrupter springs, which in turn open the motor magnet operate circuit. Motor magnet MM restores, closes the interrupter springs, and the wipers are stepped to the first bank contact (via the wiper) and the interrupter springs again energize motor magnet MM. The energized motor magnet MM opens its interrupter springs which cause motor magnet MM to restore and to step the wipers to the second bank contacts. This process is repeated at every bank contact marked by ground. When 12 TCI Library www.telephonecollectors.info the wipers are stepped to a bank contact marked by absence-of-ground, the operate circuit for motor magnet MM is incomplete and further stepping is prevented. 4 .4 .2 Ground searching (figure 18). The arrangement shown in figure 18 searches for the presence-of-ground. A start ground from a control relay's contacts or from a start key (via the break contacts of a stopping relay and the rotary switch's interrupter springs) energizes motor magnet MM. The motor magnet armature opens the interrupter springs which in turn open the motor magnet operate circuit. Motor magnet MM restores, closes the interrupter springs, and the wipers are stepped to the first bank contact. The first INT. SPGS. KEY STARJ f GROUND -=- Figure 17. Self-interrupted searching for absence-of-grou:nd. bank contact is marked by an absence-ofground and the start ground again energizes motor magnet MM. The energized motor magnet MM opens its interrupter springs which in turn cause the motor magnet MM to restore and step its wipers to the n