US2041964A - Telephone system - Google Patents

Description

G. SANDALLS. JR

TELEPHONE SYSTEM Filed Aug. 16, 1934 VINVENT-OR GSANDALLS JR ATTORNEY Patented May 26, 1936 PATENT OFFICE TELEPHONE SYSTEM George Sandalls, Jr., North Tarrytown, N. Y.,

assignor to American Telephone and Telegraph Company, a corporation of New York Application August 16,

12 Claims.

This invention relates to telephone systems and particularly to pay station service systems in which a calling subscriber must deposit a coin before he can converse with the called subscriber.

An object of this invention is to improve and simplify pay station circuits for post-payment service. Another object is to provide pay station circuits that function without any special equipment at the central office.

Heretofore systems have been provided in which a transmitter. has been disabled during certain periods of the call in which rectifiers have been used as blocking means, one in series with the transmitter and the other in parallel with the transmitter.

In these systems when a calling subscriber removes his receiver from the hook, the transmitter current is such that it may pass through the transmitter and the rectifier in series therewith. When the called party answers, the current reverses at the central oflice and the transmitter is thereby disabled as the current passes through the rectifier in shunt of the transmitter. When the called party answers the calling party can hear the answer of the called party. The calling party then deposits a coin to momentarily open a connection in shunt of a resistance in the line. This causes apparatus at the central office to reverse the current and thus permit the current to pass through the transmitter and rectifier in series therewith.

A feature of the present invention is a circuit arrangement of this type for pay station use in which rectifier means are employed to disable the transmitter by the reversal of current prior to payment and to make the transmitter operative upon payment without again reversing the current. This feature may be embodied in an arrangement where one rectifier is placed in series with the transmitter and another is placed in shunt of the transmitter and the first rectifier. Normally, the direction of current may be such that it passes through the transmitter and the rectifier in series therewith and when the called party answers the current reverses. The transmitter is thereby disabled by the current passing through the shunting rectifier. The calling party, however, can hear the answer of the called party. When the calling party then deposits a coin, the series rectifier is short circuited and the path for the shunting rectifier is opened so that without again reversing the current, the transmitter is made operative and without any rectifiers in the transmitter circuit. Thus, a talking path is provided for the calling subscriber 1934, Serial No. 740,167 (Cl. 17.96.3)

without any second reversal of. the current or any apparatus at the central office for providing such reversal. The apparatus. at the central office for reversing the current a second time as heretofore required in the prior art is thereby eliminated by the present invention and the transmitter circuit during talking is freed from all encumbrances such as the rectifier in series therewith, heretofore remaining in this circuit during talking.

Another feature is an arrangement in the above mentioned circuit whereby when the transmitter is made operative upon payment the dial or pulse contacts are eliminated from the established connection. For this purpose the dial contacts are normally placed in series with both rectifiers and the transmitter and when a coin is deposited the dial. contacts are short-circuited. This feature therefore guards the system against attempts to release an established connection and then to seize another connection without depositing another coin by manipulation of the dial contacts.

This invention will be clearly understood by reference to the accompanying drawing. The section to the right of the dotted line AA shows schematically in part a line finder LF- and other apparatus at a step-by-step dial office including a relay 25 arranged to control the reversal of current supplied to conductors 38 and 39 from a bridged impedance battery supply in connection with. coil 26. Also there is shown anabbreviated schematic representation of a connector C with contacts 48 and 49. This apparatus is all well known in the art, and only that part of it necessary to explain the operation of this invention is shown. The section to the left of said line AA illustrates a subscribers 'postpayment station arranged in accordance with this invention which includes a transmitter, receiver, induction coil, condenser, ringer, switchhoolc'and. dial. There are also illustrated two rectifiers, one of which, designated [3, is connected in series with the transmitter l2, and the other, designated I 4-, in multiple with the transmitter I2 and rectifier l3. These rectifiers are poled to pass current in the direction indicated by the arrows and to block current in the opposite direction. A coin switch is also: shown. This operates when a coin is deposited and is arranged to be locked in its operated position under control of. a hook actuated by the switchhook aforementioned.

A detailed description of the operation of' the arrangement shown in the drawing will now be given.

Assume that a subscriber at the post-payment station, hereinbefore mentioned, desires to establish a connection with another subscribers station, not shown, but connected to a dial oflice, the apparatus of which is partly shownat the right of line AA. To this end the subscriber removes the receiver 4 from the switchhook 3. This causes the line finder LE to function and close contacts 2| and 22. Other details of the line finder are not shown, the parts omitted being indicated by the dotted lines 38 and 39.

A circuit may now be traced through the contacts of dial 31 from the grounded positive pole of a battery connection established by the line finder, not shown, line finder contact 22, over conductor 42, through switchhook contact 3, transmitter l2, rectifier I3, conductor 4|, springs l8 and II of dial 3|, over conductor 48, winding I of induction coil 36, through line finder contact 2|, to the negative pole of said battery. In the circuit above traced current flows in the direction of the arrow of rectifier l3, and consequently rectifier |3 permits current to pass through itself and transmitter l2. In shunt with transmitter l2 and rectifier I3 a circuit path may be traced through rectifier l4 and coin switch springs l9 and I1.

Through this shunt path, however, no appreciable current can flow at this time, since the direction of fiow opposes the direction of the arrow of rectifier l4. This high resistance path through rectifier I4 is only indicidental at this time. However, its useful functioning will be described later in another connection. It is sufficient for the present that the path through transmitter l2 be of low resistance, as evidenced by the passage of current therethrough as described above, so that other apparatus, not shown, at the dial office may be caused to function and to extend a talking connection through connective apparatus in the dial office leading towards the line of the called subscriber, such apparatus consisting of automatic switches and relays, which are not shown here, The subscriber on receiving the usual dial tone, now operates dial 31 and dials the number of the called subscriber. This causes pulsing contacts l8 and H to interrupt a circuit which was in part previously traced. This circuit was hereinbefore traced from a grounded positive pole of a battery connection to switchhook contact 6. From this point the pulsing circuit proceeds through switchhook contact 5 and off normal contacts 8 and 9 (which are closed when the dial is moved from its normal position) through pulsing contacts I0 and H and thence over conductor 48 by the circuit previously traced to the negative pole of said battery. To avoid clicks in the receiver 4 while dialing dial contacts and 8 are opened while the dial is off normal, thereby opening the circuit through winding 2 of induction coil 36 and the winding of receiver 4.

The interruptions in accordance with dial pulses of the pulsing circuit corresponding to the digits of the called number eventually effect a connection from battery 44, windings of coil 26, conductors 21 and 3|, contacts 28 and 32 of relay 25, conductors 38 and 39, contacts 2| and 22 at the line finder, through the calling subscribers loop as hereinbefore traced, and also a connection through condensers 23 and 24 and conductors 33 and 34 to the called subscribers line, not shown. When the receiver at the called station is removed from the switchhook, a bridge not shown, is connected across conductors 33 and 34, causing the operation of relay 25, through a circuit which may be traced from grounded battery 45 through the upper winding of relay 25 to conductor 34, thence through said bridge, over conductor 33 and through the lower winding of relay 25 to ground. Relay 25 in operating reverses the polarity of the current connected to line finder contacts 2| and 22 from battery 44 and a circuit may now be traced, in the direction of current flow from the grounded positive pole of battery 44, through the lower winding of coil 26, through contacts 29 and 28 of relay 25, conductor 38, line finder contact 2|, through winding of induction coil 38 conductor 48, contacts H and H) of dial 31, over conductor 4| to rectifier I3, which is poled so as to prevent the passage of current through it and transmitter l2. However, from junction point 43, the circuit may be continued through contacts H and 9 and rectifier M to switchhook contact 6. Rectifier I4 is so poled that current is now passed through it, and accordingly it acts as a low resistance shunt on the series path consisting of rectifier |3 and transmitter i2. From switchhook contact 6 the circuit continues over conductor 42 through line finder contacts 22, conductor 39, contacts 32 and 30 of relay 25 and upper winding of coil 26 to negative pole of battery 44. From the circuit just traced it is seen that the reversal of current due to the answer of the called subscriber has caused the disabling of transmitter l2, since as explained hereinbefore current is now blocked by the opposing rectifier |3 from passing through 2 transmitter |2 while the rectifier I4 is so connected as to act as a low resistance shunt on the series path including rectifier |3 and transmitter I2. Although the transmitter I2 is thus rendered inefiective receiver 4 is so connected that the subscriber at the post-payment station can hear the answer of the called subscriber over the line through the normal receiver circuit comprising condenser 20, winding 2 of induction coil 33, receiver 4, normally closed dial contacts I and 8, switchhook contacts 5 and 6 and conductor 42.

It is now necessary for the calling subscriber, in order to put the line in a conversational condition, to deposit a coin 43, the weight of which causes springs I5, I! and I8 to make contact and spring I! to break its normal contact with spring IS. The effect of this is to make the transmitter effective for conversation, as will now be seen. It was explained hereinbefore that when the called subscriber answered and the current was reversed that the passage of current through transmitter |2 was blocked by rectifier l3, and that the transmitter was further disabled by a shunting path through rectifier I4, which freely passe-d the shunting current under this condition. When springs l5 and Il make contact it is seen that rectifier I3 is short-circuited over an obvious circuit and that the shunt due to rectifier I4 is opened when springs I9 and I1 break. Consequently, current can now pass through transmitter l2 over a circuit path from conductors 48 and 41, through springs l8, l1 and I5, transmitter l2, switchhook contact 6 to conductor 42, and thence over the circuit previously traced. When the subscriber at the pay station talks, current in the primary winding of induction coil 36 fluctuates in accordance with the sound waves impressed on the diaphragm of transmitter I2, inducing corresponding cur rents in secondary winding 2, which are conducted to the line in the usual manner through condenser 28, winding 2, receiver 4, dial contacts 1 and 8, and switchhook contacts 5 and 6. When spring |5 was depressed by the deposit of coin 43 it locked in its operated position under control of spring 'fB, which moved to the left when the receiver 4 was removed from the switchhook 3.

At. the end of the conversation receiver 4 is restored to switchhook 3, which causes contacts 5 and 6 to open and release the apparatus at the central ofiice, and also spring I6 to move to the right releasing spring !5. The motion of spring It also causes coin 43 to be removed from spring l5, thereby restoring springs l5, ll, 48 and I9 to their normal position. It Will be noted that when springs I5, I1, I 8 and I 9 are still in their operated position before the coin 43 is removed by restoring the receiver 4 to the switchhook 3, the apparatus at the central oflice cannot be released by moving the dial contacts oif normal, since the dial contact springs it and H are disabled over a shunt path including conductor 41, springs l8 and 1, and conductor 4!. It is thus impossible to dial another number without first disposing of the deposited coin 43 by restoring the receiver 4 to the switchhook 3.

The preceding description is for a call requiring the deposit of a coin. A description will now be made for the case where the pay station subscriber wishes to call an ofiicial number, for which nocharge is to be made. In this case the subscriber dials the desired number as previously described and when the called party answers there is no reversal of line current and the current passes through transmitter. 62 over the circuit previously traced in connection with an outgoing call for a subscriber, before said subscriber answered and reversed the current. Consequently it is now unnecessary to deposit a coin to converse with the called party.

A call incoming from the central oifice will now be described. When the calling subscriber (whose station is not shown) dials the number of the pay station, connection is made to the called line over conductors 5B, 53, 52 and 5| and contacts 48 and 49 of an automatic connector C, the details of which are well known in the art and consequently need not be shown here. The omitted portions are indicated by the dotted lines representing conductors 5s, 53, 52 and 5:1. As soon as a connection is established ringing current is applied and a circuit may be traced from one terminal of the source of ringing current (not shown) over conductor 50 through contact 48, over conductor 53, through ringer 35, condenser 20, over conductor 52, through contact 49 and over conductor 5| to the other ringing terminal (not shown). Ringer 35 sounds when the subscriber in answering removes receiver 4 from the switchhook a bridge is closed, which causes the ringing current to be disconnected. This bridge is the same as that previously traced through the apparatus of the subscribers station for an outgoing call, before the called station answered and reversed the current. After ringing has ceased, battery and ground (not shown) are connected to conductors 5t and 5| respectively. It is assumed that the battery terminal is negative and the ground terminal positive. Current will now flow through contacts 48 and 49 of connector C and over conductors 53 and 52 through a circuit at the sub scribers station, including transmitter l2 that was previously traced for a call outgoing from the pay station before current was reversed by the answer of the called subscriber. The station is now ready for conversation through contacts 48 and 49 of connector C and over conductors 5i] and 5|. At the end of the conversation, the

called subscriber replaces receiver 4 on the switchhook 3, and when the calling subscriber also disconnects the connection is broken down at contacts 48 and 49 of connector C, restoring all apparatus to normal.

What is claimed is:

1. A telephone set comprising a microphone, a circuit therefor, rectifier means in said circuit for short-circuiting said microphone during a certain period of a call from said set, and means for entirely eliminating said rectifier means from said circuit during other periods of said call.

2. A telephone set comprising a microphone, a circuit for said microphone, rectifiers in said circuit effective on current reversal in said circuit while making a call from said set for short-circuiting said microphone, and means thereafter operative for entirely excluding said rectifiers from said circuit to permit said reversed current to pass through the microphone.

3. A telephone set comprising a microphone, a circuit therefor, a rectifier in said circuit in series with said microphone, a rectifier in said circuit in parallel with said microphone and said first mentioned rectifier, and means operative upon payment for shunting the rectifier in series with the microphone and for opening the connection in said circuit for the rectifier in parallel with the microphone.

4. A telephone set comprising a microphone and a dial, a circuit for said microphone and dial, rectifier means in said circuit for short-circuiting said microphone during a certain period of making a call from said set, and means for eliminating said rectifier means from said circuit and shortcircuiting said dial during other periods of said call.

5. A telephone set comprising a microphone and a dial, a circuit therefor, rectifiers in said circuit efiective on current reversal in said circuit while making a call from said set for shortcircuiting said microphone, and means thereafter operative for entirely excluding said rectifiers from said circuit to permit said reversed current to pass through the microphone.

6. A telephone set comprising a microphone and dial contacts, a circuit for said microphone and dial contacts, rectifier means in said circuit for preventing the passage of current through said microphone during a call from said set, and means for entirely eliminating said rectifier means from said circuit to allow passage of currents through said microphone during certain other periods of said call.

7 A telephone pay station comprising a microphone and dial contacts, a circuit for said microphone and dial contacts, rectifier means in said circuit for blocking of speech current of one direction through the microphone prior to payment and means for eliminating said rectifier means and dial contacts from said circuit upon payment to permit the passage of speech current of said direction through the microphone.

8. A telephone pay station comprising a microphone, dial contacts, rectifiers, a circuit including one of said rectifiers in series with said microphone and another of said rectifiers in shunt of said microphone and said first mentioned rectifier and said dial contacts in series with said rectifiers and microphone, said first mentioned rectifier blocking current of one direction through said microphone and said second mentioned rectifier passing current of said one direction in shunt of the microphone, and means responsive upon payment for eliminating said rectifiers and said dial certain period of a contacts from said circuit to sage of current of said one the microphone.

9. A telephone pay station comprising a microphone, dial contacts, two rectifiers, a circuit for connecting one rectifier in series and the other in parallel with said microphone and both rectifiers in series with said dial contacts, means operative prior to payment for preventing current from passing through said microphone by the aid of said rectifiers, and means operative upon payment for permitting the passage of current through said microphone without passing through said rectifiers and said dial contacts.

10. A telephone pay station comprising a circuit, a microphone in said circuit, a rectifier in said circuit in series with said microphone, a rectifier in said circuit in parallel with said microphone and said first mentioned rectifier, dial contacts in series with one of said rectifiers, and means operative upon payment for shunting the rectifier in series with the microphone for opening said circuit for the rectifier in parallel with the microphone and for shunting the dial contacts.

11. In a telephone pay station, a microphone, two rectifiers, pulsing and off-normal dial contacts, switchhook contacts, coin operated contacts, a circuit arrangement for establishing a talking connection effective on the operation of the switchhook contacts, a circuit arrangement for establishing a dialing connection effective on the operation of the off -normal contacts, a circuit arrangement effective on the reversal of current to the pay station for preventing a current passing through the microphone, said circuit arrangement including one rectifier blocking the passage of said current through the microphone and the permit free pasdirection through other rectifier by-passing said current past the microphone and a circuit arrangement effective on the operation of the coin operated contacts for establishing a talking connection through the microphone without again reversing the current.

12. In a telephone pay station, a microphone, two rectifiers, pulsing and ofi-normal dial contacts, switchhook contacts, coin operated contacts, a circuit arrangement for establishing a talking connection effective on the operation of the switchhook contacts including the pulsing contacts, a first rectifier, the microphone and the switchhook contact in series, a circuit arrangement for establishing a dialing connection effective on the operation of the off-normal contacts, said connection including the dialing contacts, the ofi-normal contacts and the switchhook contacts in series, a circuit arrangement effective on the reversal of current to the pay station, for blocking the passage of said current through the microphone, including the pulsing contacts, certain of the coin operated contacts, the second rectifier and the switchhook contacts in series with said second rectifier in the current passing direction and the microphone and the first rectifier in series with said first rectifier in the current blocking direction, and a circuit arrangement effective on the operation of the coin operated contacts for establishing a talking connection through the microphone without again reversing the current, including the opening of the connection for the second rectifier and shortcircuiting the pulsing contacts and the first rectifier and the closing of a connection through the microphone through certain of the coin operated contacts and the switchhook contacts only.

GEORGE SANDALLS, JR.

DISCLAIMER 2,041,964.Ge0rge Sandalls, J12, North Tarrytown, N. Y. TELEPHONE SYSTEM. Patent dated May 26, 1986. Disclaimer filed May 29, 1937, by the assignee,

American Telephone and Telegraph Company. I Hereby enters this disclaimer to claims 3 and 11 of the above numbered patent.

[Ofiic'ial Gazette, June 22, 1937.]

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