US2425820A - Selective system - Google Patents
Selective system Download PDFInfo
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- US2425820A US2425820A US522849A US52284944A US2425820A US 2425820 A US2425820 A US 2425820A US 522849 A US522849 A US 522849A US 52284944 A US52284944 A US 52284944A US 2425820 A US2425820 A US 2425820A
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- 238000004804 winding Methods 0.000 description 13
- 230000005540 biological transmission Effects 0.000 description 9
- 239000004020 conductor Substances 0.000 description 9
- 238000010586 diagram Methods 0.000 description 5
- 230000011664 signaling Effects 0.000 description 4
- 241001123248 Arma Species 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q1/00—Details of selecting apparatus or arrangements
- H04Q1/18—Electrical details
- H04Q1/30—Signalling arrangements; Manipulation of signalling currents
- H04Q1/38—Signalling arrangements; Manipulation of signalling currents using combinations of direct currents of different amplitudes or polarities over line conductors or combination of line conductors
Definitions
- Glaimsi 1.1 This inventionrelates to signaling systems and moreparticularly to systems providing for selective'signaling' and is a continuation in part of application Serial No. 441423; filedJunel 'l I942.
- a signaling circuit would be provided between. two oihces and. means, such as telephone dial equipment, would be providedat one oihce for opening or interrupting the signaling circuit to send code signals. thereover tothe other ofilce; At the other oilice there would be provided a selector switch and a plurality of relays for corn trolling the selector switch in response tothe code signals.
- the selector switch would have a bank of contacts with relays individual to-certain of said contacts. Each of these relaysmight have a. plurality of armatures which would be connected individually to the contacts in said bank other than the contact'to which their relay was connected.
- each of nine of the contacts of a bank of ten contacts might have a relay individually connected thereto and each relay might be provided with" eight arma tures. connected individually to the remaining eight contacts to which their-relay'was not connected.
- the arrangements of the. invention would provide a; simple method of selecting at least seventy-two different signal lines in response to correspondingcod'e combinations of. a three digit code.
- Fig. 1 is a circuit diagram illustrating certain. principles of operation of the invention.
- Fig. 2 is a circuit diagram illustrating certain other principles of operation of the invention.
- Fig; 3 is a circuit diagram illustrating in more detail how the arrangementsof the invention could be utilized to select anyone of a large number of lines, such, for example, as seventy-two lines. Simil r reference characters have been utilized to denote like parts in all offthe figures.
- Fig. 1 is showna.
- line I I which would terminate at a distant station (not shown).
- apparatus such as telephone dialing equipment whereby the line could be opened or interrupted as desired, so as to transmit code signals over the line.
- apparatus such as telephone dialing equipment whereby the line could be opened or interrupted as desired, so as to transmit code signals over the line.
- At the station to be ca'lledthere would bepr'ovided'a number of relays and-selector mech- SeriaPNo. 5222849 anismtopick out the r be selected: pa ticular signal circuit to line [L and isthereover.
- Relay I 2 controls the operation of relay M which is aslow-release relay;
- Relay" l2 also controls the operation of a rotor magnet l5 arm Fl over thecontacts l toi Ill-tea bank of contacts.
- relay l2 will also closethe following circuit. From ground battery It, armature and contact of relay l2: winding of rotormagnet l5to ground: Accordingly, every time relay l2 releases, due to interruptions of the line caused by the transmission of a digit of the code signal, rotor magnet l5 will step its contact arm ahead" one step. If it be assumed that the digit of the code signal beingsentis 'fi", the contact arm I! will be moved ahead tocontact 5 of the selector bank.
- relay I l Due tothefact that relay I l is slow-release it will remain operated during'these five interruptions of the iinecaused' by the transmission of the digit 5 ofthe code signal; The interval between this digit 5 and the next digit" of the code signal to transmitted will, however, be long enough for slow-releaserelay it" to release and close the foilcwingcircuit. From'ground, battery 26, armature'and contact of relay I i; contact arm l1, contact 5, conductor 2t, contact of relay 58, winding of relay 58 toground. This will operate rel'ay Mend it will lock. up over its contact and armature through battery I9 to ground.
- relay I4 will also close a circuit from battery 26, through the winding of release magnet Hi to ground and will operate release magnet I6 which will return the contact arm to its zero position.
- the relay 58 is a slow-operate and slow-release relay and the release magnet I6 is adjusted to operate slightly slower than relay 58. Under these conditions when the contact arm rests on contact 5 relay 58 will have time to operate and lock up before the release magnet I6 returns the contact arm to its Zero position. Furthermore, when the rotor magnet I5 is stepping the contact arm I'I ahead, or when the release magnet I6 operates and returns the contact arm I!
- Conductor 23 will be the circuit selected by the code signal heretofore mentioned, and it may terminate in a lock-up signal (not shown) of any desired type.
- the release magnet is will subsequently operate and will return contact arm IT to its zero position.
- the digit 1 is always the first digit of the code signal to be sent over the line. This would step contact arm II to position I.
- In the ensuing interval between digits of the code signal relay I i would release and would place like poles of batteries 26 and I9 across the winding of relay 58 effectively short-circuiting it and causing it to release.
- each code signal used to select a line should start with the digit 1 and would then be followed by other digits of the code signal.
- relay 58 is a slow-release relay. Accordingly, when a code signal such as 5 is sent over the line and the release magnet I6 allows the contact arm to return over contacts 2, 3, 2, I, successively, the interval that the contact arm remains on contact I in so returning to its zero position will not be long enough to release relay 58.
- Fig. 2 is shown a circuit diagram illustrating other principles of operation of the invention.
- Fig. 1 only one relay, such as 58, with a plurality of armatures was shown connected to the selector mechanism.
- Fig. 2 is shown how additional relays, such as 4 8, could be connected to other of the contacts of the bank.
- the connections for relay 58 are the same as heretofore described with respect to Fig. 1.
- Relay 48 has one end of its winding connected by conductor 29 to contact 4 of the bank.
- Fig. 3 is shown a more complete circuit diagram illustrating how the arrangements of the invention could be utilized to select any one of a large number of lines, such for example as seventy-twolines.
- the contacts I to Ill respectively of the bank of contacts of the selector mechanism.
- the apparatus for responding to the code signals transmitted over the line II such as relays l2 and I4 and rotor magnet I5 and release magnet I6 operates as heretofore described with respect to Fig 1.
- relay 28 is shown with one end of its winding connected to contact I and the other end of its winding connected to contact 2. It might be provided with eight armatures with which would be associated eight lines to be selected.
- any one of the eight lines associated with the armatures of relay 28 may be selected by using the following three digit code signals:
- Relay 38 is shown with one end of its winding connected to contact I and the other end of its winding connected to contact 3. It might be provided with eight armatures with which would be associated eight lines to be selected. These armatures would be connected to contacts of the bank other than contact 3 to which relay 38 is connected and other than contact I which is commonly used for release purposes. Any one of the eight lines associated with the armatures of relay 38 may be selected by using the following three digit code signals:
- Another relay ill is shown with one end of its winding connected to contact l and the other end of its Winding connected to contact l. It too might be provided with eight armatures and eight associated lines. In this case the armatures would be connected to contacts in the bank other than contacts l and l. Any one of the lines associated with the armatures of relay 38 may be selected by using the following three digit code signals:
- a selective system comprising a line over which code combinations comprising groups of impulses are transmitted, a station connected to said line, selective mechanism including a bank of terminals and a contact arm therefor at said station, said contact arm having a normal position, a plurality of relays each connected individually to a diiferent one of the terminals of said bank, a plurality of contacts individual to each of said relays, each of said contacts being connected individually to terminals in said bank other than the terminal to which its individual relay is connected, a plurality of circuits to be selected individual to each of said relay contacts, means responsive to the reception at said station of a group of impulses of a transmitted code combination to cause said contact arm to rest on any desired terminal to which any of said relays is connected to operate the relay connected thereto, means responsive to the subsequent reception of another group of impulses of the transmitted code combination to cause said contact arm to rest on any desired terminal to which is connected 2. contact individual to the previously operated relay to complete the circuit individual to the contact connected to such terminal, and means whereby the contact arm is returned to normal
- a selective system comprising a 1ine over which groups of impulses are transmitted, a station connected to said line, selective mechanism including a bank of terminals and a contact arm therefor at said station, said contact arm having a normal position, a plurality of relays each connected individually to a different one of the ter minals of said bank, a plurality of contacts individual to each of said relays, each of said contacts being connected individuall to terminals in said bank other than the terminal to which its individual relay is connected, a plurality of circuits to be selected individual to each of said relay contacts, means responsive to the reception at said station of a group of impulses to operate any desired one of th relays connected to said terminals, means responsive to the subsequent reception at said station of another group of impulses to complete any desired one of the circuits individual to any of the contacts individual to the relay previously operated by said first group of impulses, means responsive to the subsequent reception at said station of another group of impulses to release the previously operated relay and means whereby the contact arm is returned to normal after the termination of each group of impulses
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Description
Aug; 1947- J. T. NEISWINTER 2,425,820
SELECTIVESYSTEM F led Feb. 17, 1944 2 Sheets-Sheet 1 Slow o operate 10 o Slow operate w rekase Slow opera/ta Slow release 0 --o Slow ope/ante L Slow release ao INVENTOR ATTORNEY Aug- 19, 1947, J. T. NEISWINTER 2 4 5 SELECTIVE SYS-TEM Fi l ed Feb. 17, 1944 2 Sheets- Sheet 2 Flow qverate INVENTOR J ZZWmwinte/r TTORNEY Patented Aug. 19, 1947 James '1 Neiswinter; South Orange, N. -Jl,
assignorto American Telephonoandc'l elegraph Come party, a corporation of New York.-
Application February 17, 1944;
2 Glaimsi 1.1 This inventionrelates to signaling systems and moreparticularly to systems providing for selective'signaling' and is a continuation in part of application Serial No. 441423; filedJunel 'l I942.
In the. arrangements of the invention a signaling circuit would be provided between. two oihces and. means, such as telephone dial equipment, would be providedat one oihce for opening or interrupting the signaling circuit to send code signals. thereover tothe other ofilce; At the other oilice there would be provided a selector switch and a plurality of relays for corn trolling the selector switch in response tothe code signals. The selector switch would have a bank of contacts with relays individual to-certain of said contacts. Each of these relaysmight have a. plurality of armatures which would be connected individually to the contacts in said bank other than the contact'to which their relay was connected. For example, each of nine of the contacts of a bank of ten contacts might havea relay individually connected thereto and each relay might be provided with" eight arma tures. connected individually to the remaining eight contacts to which their-relay'was not connected. Withsuch connections the arrangements of the. invention would provide a; simple method of selecting at least seventy-two different signal lines in response to correspondingcod'e combinations of. a three digit code. Other objects and features of the invention will appear more fully from the detailed description thereof hereinafter given.
The invention may be more fully understood from the following description together with the aecompanyingdrawing in the Figures 1, 2. and 3 of which the invention is illustrated. In. Fig. 1 is a circuit diagram illustrating certain. principles of operation of the invention. In Fig. 2 is a circuit diagram illustrating certain other principles of operation of the invention. In Fig; 3 is a circuit diagram illustrating in more detail how the arrangementsof the invention could be utilized to select anyone of a large number of lines, such, for example, as seventy-two lines. Simil r reference characters have been utilized to denote like parts in all offthe figures.
In Fig. 1 is showna. line I I which would terminate at a distant station (not shown). At the distant station there would be provided apparatus (not shown) such as telephone dialing equipment whereby the line could be opened or interrupted as desired, so as to transmit code signals over the line. At the station to be ca'lledthere would bepr'ovided'a number of relays and-selector mech- SeriaPNo. 5222849 anismtopick out the r be selected: pa ticular signal circuit to line [L and isthereover. Relay I 2 controls the operation of relay M which is aslow-release relay; Relay" l2 also controls the operation of a rotor magnet l5 arm Fl over thecontacts l toi Ill-tea bank of contacts. A release magnet I 6" is also provided. Connected to one of the 1=. il heseare connected to contacts in the bank by the code-signal sent thereover relay l2 releases and closes the following circuit. From ground, battery [3, armature and contact of relay I 2,
nal 'sent thereover; The-release of relay l2 will also closethe following circuit. From ground battery It, armature and contact of relay l2: winding of rotormagnet l5to ground: Accordingly, every time relay l2 releases, due to interruptions of the line caused by the transmission of a digit of the code signal, rotor magnet l5 will step its contact arm ahead" one step. If it be assumed that the digit of the code signal beingsentis 'fi", the contact arm I! will be moved ahead tocontact 5 of the selector bank. Due tothefact that relay I l is slow-release it will remain operated during'these five interruptions of the iinecaused' by the transmission of the digit 5 ofthe code signal; The interval between this digit 5 and the next digit" of the code signal to transmitted will, however, be long enough for slow-releaserelay it" to release and close the foilcwingcircuit. From'ground, battery 26, armature'and contact of relay I i; contact arm l1, contact 5, conductor 2t, contact of relay 58, winding of relay 58 toground. This will operate rel'ay Mend it will lock. up over its contact and armature through battery I9 to ground. The release of relay I4 will also close a circuit from battery 26, through the winding of release magnet Hi to ground and will operate release magnet I6 which will return the contact arm to its zero position. The relay 58 is a slow-operate and slow-release relay and the release magnet I6 is adjusted to operate slightly slower than relay 58. Under these conditions when the contact arm rests on contact 5 relay 58 will have time to operate and lock up before the release magnet I6 returns the contact arm to its Zero position. Furthermore, when the rotor magnet I5 is stepping the contact arm I'I ahead, or when the release magnet I6 operates and returns the contact arm I! to its zero position, the speed with which it will pass over other contacts such as 4, 3, 2, etc., to which other slow-operate, slowrelease relays similar to 58 might be connected, will be such that the slow-operate, slow-release relays will not be operated and locked up. Let it be assumed that the next digit being sent in the code signal is '7. The contact arm which has been returned to its zero position will now be moved around to contact I and the interval following the transmission of such digit will be long enough for slow-release relay I4 to release. This will connect battery 26 to contact arm I'l, contact l, and thence over conductor 22 and the armature and contact of relay 58 to conductor 23. Conductor 23 will be the circuit selected by the code signal heretofore mentioned, and it may terminate in a lock-up signal (not shown) of any desired type. The release magnet is will subsequently operate and will return contact arm IT to its zero position. In order to select other lines it would first be necessary to release the locked up relay 58. To do this the digit 1 is always the first digit of the code signal to be sent over the line. This would step contact arm II to position I. In the ensuing interval between digits of the code signal relay I i would release and would place like poles of batteries 26 and I9 across the winding of relay 58 effectively short-circuiting it and causing it to release. Ac-
cordingly, each code signal used to select a line should start with the digit 1 and would then be followed by other digits of the code signal. As
will be pointed out hereinafter, all of the other 7 relays such as 58 individual to contacts of the bank would have their windings connected by conductors similar to 2I to the contact I of the bank. Accordingly, the use of the digit 1 as the first digit of each code signal, would release any of the relays such as 58 which had previously been locked up and would prevent false operation of the arrangements. As heretofore pointed out, relay 58 is a slow-release relay. Accordingly, when a code signal such as 5 is sent over the line and the release magnet I6 allows the contact arm to return over contacts 2, 3, 2, I, successively, the interval that the contact arm remains on contact I in so returning to its zero position will not be long enough to release relay 58. However, when the digit 1 of the code signal is sent, the fact that release magnet I6 is slowoperate, as heretofore pointed out, will allow the contact arm I1 to remain on contact I long enough to release relay 5%. To select another line by means of relay 53 and another of its armatures, the code signal 1, 5, 6 might be sent. As heretofore pointed out, the transmission of the digit 1 would release relay 5% and any other relays similar to it that had been operated. The transmission of digit 5 would cause relay 58 to operate and become locked up in the manner heretofore described. The subsequent transmission of the digit 6 would advance the contact arm I? to contact 6 and would connect battery 25 to conductor 2d, the second armature of relay 5-8 and thence to conductor 25, thus causing line 25 to be selected.
In Fig. 2 is shown a circuit diagram illustrating other principles of operation of the invention. In Fig. 1 only one relay, such as 58, with a plurality of armatures was shown connected to the selector mechanism. In Fig. 2 is shown how additional relays, such as 4 8, could be connected to other of the contacts of the bank. The connections for relay 58 are the same as heretofore described with respect to Fig. 1. Relay 48 has one end of its winding connected by conductor 29 to contact 4 of the bank. As heretofore pointed out the other end of its winding (as would be the case with all similar relays) would be connected to contact I of the bank so that if it had previously been operated and locked up the transmission of digit 1, which starts every one of the code signals used, would cause it to release. To select the lines 32 and 3% shown associated with the armature of relay 48 the code signals 1-4-6 and 1-4-7 would be used respectively. As pointed out previously the digit 1 would release any of the relays, such as 58 or 38, which had previously been operated. The transmission of digit 4 would cause relay as to operate and lock up. The transmission of digits 6 or '7 would put battery 26 on lines 32 or 34 respectively by means of the armatures and contacts of relay 43 to cause them to be selected.
In Fig. 3 is shown a more complete circuit diagram illustrating how the arrangements of the invention could be utilized to select any one of a large number of lines, such for example as seventy-twolines. In Fig. 3 are shown the contacts I to Ill respectively of the bank of contacts of the selector mechanism. The apparatus for responding to the code signals transmitted over the line II such as relays l2 and I4 and rotor magnet I5 and release magnet I6 operates as heretofore described with respect to Fig 1. In Fig. 3 relay 28 is shown with one end of its winding connected to contact I and the other end of its winding connected to contact 2. It might be provided with eight armatures with which would be associated eight lines to be selected. These armatures would be connected to contacts of the bank other than contact 2 to which relay 28 is connected and other than contact I which is commonly used for release purposes. In other words the armatures of relay 28 would be connected to the contacts 3 to It inclusive. As will appear from the description of the operation heretofore given any one of the eight lines associated with the armatures of relay 28 may be selected by using the following three digit code signals:
Another relay ill is shown with one end of its winding connected to contact l and the other end of its Winding connected to contact l. It too might be provided with eight armatures and eight associated lines. In this case the armatures would be connected to contacts in the bank other than contacts l and l. Any one of the lines associated with the armatures of relay 38 may be selected by using the following three digit code signals:
In a similar manner other relays each with a plurality of armatures and associated lines to be selected might be connected to other contacts in the bank by means of conductors such as 50 and 53'. By providing ten contacts and havlngnine relays, each with eight contacts, the arrangements of the invention provide a means for selecting any one of seventy-two lines. However, in accordance with the principles of the invention the number of contacts in the bank, the associated relays and the number of armatures to each relay might be increased or decreased from the number shown to select a greater or lesser number of lines.
Accordingly while the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable it is understood that it is capable of embodiment in many and other widely varied forms without departing from the spirit of the invention as defined by the appended claims.
What is claimed is:
1. A selective system comprising a line over which code combinations comprising groups of impulses are transmitted, a station connected to said line, selective mechanism including a bank of terminals and a contact arm therefor at said station, said contact arm having a normal position, a plurality of relays each connected individually to a diiferent one of the terminals of said bank, a plurality of contacts individual to each of said relays, each of said contacts being connected individually to terminals in said bank other than the terminal to which its individual relay is connected, a plurality of circuits to be selected individual to each of said relay contacts, means responsive to the reception at said station of a group of impulses of a transmitted code combination to cause said contact arm to rest on any desired terminal to which any of said relays is connected to operate the relay connected thereto, means responsive to the subsequent reception of another group of impulses of the transmitted code combination to cause said contact arm to rest on any desired terminal to which is connected 2. contact individual to the previously operated relay to complete the circuit individual to the contact connected to such terminal, and means whereby the contact arm is returned to normal after the termination of each group of impulses.
2 A selective system comprising a 1ine over which groups of impulses are transmitted, a station connected to said line, selective mechanism including a bank of terminals and a contact arm therefor at said station, said contact arm having a normal position, a plurality of relays each connected individually to a different one of the ter minals of said bank, a plurality of contacts individual to each of said relays, each of said contacts being connected individuall to terminals in said bank other than the terminal to which its individual relay is connected, a plurality of circuits to be selected individual to each of said relay contacts, means responsive to the reception at said station of a group of impulses to operate any desired one of th relays connected to said terminals, means responsive to the subsequent reception at said station of another group of impulses to complete any desired one of the circuits individual to any of the contacts individual to the relay previously operated by said first group of impulses, means responsive to the subsequent reception at said station of another group of impulses to release the previously operated relay and means whereby the contact arm is returned to normal after the termination of each group of impulses.
JAMES T. NE'ISWINTER.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,695,908 White Dec. 18, 1928 1,709,031 McCoy Apr. 16, 1929 1,885,214 Almquist Nov. 1, 1932 2,063,354. Thorp Dec. 8, 1936 2,226,692 Brunner Dec, 31, 1940
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US522849A US2425820A (en) | 1944-02-17 | 1944-02-17 | Selective system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US522849A US2425820A (en) | 1944-02-17 | 1944-02-17 | Selective system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2425820A true US2425820A (en) | 1947-08-19 |
Family
ID=24082632
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US522849A Expired - Lifetime US2425820A (en) | 1944-02-17 | 1944-02-17 | Selective system |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US2425820A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2563127A (en) * | 1948-04-21 | 1951-08-07 | Stephen Baker S | Selector calling system |
| US2671167A (en) * | 1946-12-21 | 1954-03-02 | Hammarlund Mfg Company | Selective calling system |
| DE973402C (en) * | 1955-01-27 | 1960-02-18 | Sueddeutsche Telefon App | Circuit arrangement for telecommunications, especially telephone systems with rotary dials, which are provided with locking points |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1695908A (en) * | 1928-12-18 | Supervisory control system | ||
| US1709031A (en) * | 1924-05-22 | 1929-04-16 | Westinghouse Electric & Mfg Co | Supervisory control system |
| US1885214A (en) * | 1932-03-18 | 1932-11-01 | American Telephone & Telegraph | Signaling system |
| US2063354A (en) * | 1931-03-16 | 1936-12-08 | Bell Tel Phone Lab Inc | Selective calling circuits |
| US2226692A (en) * | 1938-03-11 | 1940-12-31 | Bendix Radio Corp | Control system |
-
1944
- 1944-02-17 US US522849A patent/US2425820A/en not_active Expired - Lifetime
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1695908A (en) * | 1928-12-18 | Supervisory control system | ||
| US1709031A (en) * | 1924-05-22 | 1929-04-16 | Westinghouse Electric & Mfg Co | Supervisory control system |
| US2063354A (en) * | 1931-03-16 | 1936-12-08 | Bell Tel Phone Lab Inc | Selective calling circuits |
| US1885214A (en) * | 1932-03-18 | 1932-11-01 | American Telephone & Telegraph | Signaling system |
| US2226692A (en) * | 1938-03-11 | 1940-12-31 | Bendix Radio Corp | Control system |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2671167A (en) * | 1946-12-21 | 1954-03-02 | Hammarlund Mfg Company | Selective calling system |
| US2563127A (en) * | 1948-04-21 | 1951-08-07 | Stephen Baker S | Selector calling system |
| DE973402C (en) * | 1955-01-27 | 1960-02-18 | Sueddeutsche Telefon App | Circuit arrangement for telecommunications, especially telephone systems with rotary dials, which are provided with locking points |
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