WO1998007271A1

WO1998007271A1 - Improvement introduced in semi-public telephones

Info

Publication number: WO1998007271A1
Application number: PCT/BR1997/000040
Authority: WO
Inventors: Edson BORTOLLI JÚNIOR; Salomão Abud GREGÓRIO; José Mario TAGLIASSACHI; Noberto Alves Ferreira; João Luis COELHO; Newton Bomeisel Cardoso; Marcos Assano; Rosana Jamal Francisco Dos Santos Fernandes
Original assignee: Telecomunicacoes Brasileiras S/a - Telebras
Current assignee: Telecomunicacoes Brasileiras S/a - Telebras
Priority date: 1996-08-14
Filing date: 1997-08-12
Publication date: 1998-02-19
Anticipated expiration: 1999-02-14
Also published as: BR9604099A; BR9604099C1

Abstract

A card-operated semi-public telephone (20) connected to a conventional telephone line (12) composed by a metal wire pair, in which travels a digital signal formed by the multiplexation of two digital voice channels and a control channel. This telephone is provided with demultiplexing means (41) which separate the two channels. The first one is used by the card-operated telephone itself and the second one is sent, through an analog interface (46), to a second apparatus (20) of the subscriber conventional type. Both channels are independent and each apparatus has its own dialling number.

Description

SPECIFICATION IMPROVEMENT INTRODUCED IN SEMI-PUBLIC TELEPHONES The present invention refers to the telecommunication area, and more specifically, to public telephones operated by tokens, cards or the like.. Public telephones operated by metal tokens or cards are already well known and widely used. In these telephones the billing of calls is made in the telephone apparatus itself, as opposed to what happens with subscriber telephones, in which calls are billed at the central switching exchange.

One of the drawbacks of the telephones placed indoors, such as in shops, is their low amount of utilization, which results in under-use of the network, which was designed for heavier traffic. This problem can be reduced by the use of semi-public telephones (STP), in which the use of the terminal is shared between the owner (the subscriber) and users going to the shop. The subscriber can select the operating mode by means of a switch: in the SUBSCRIBER position, all types of calls are accepted - local, regional, long-distance or international. It is also possible to make and receive collect calls. With the switch in the PUBLIC position, only local and regional calls with the use of tokens/cards are allowed and it is also possible to make collect calls. For collecting purposes, all calls both in the SUBSCRIBER position as in the PUBLIC position made from the telephone apparatus are billed at the central exchange and the telephone bill is paid fully by the subscriber, with a 25% discount. The compensation of the cost related to calls made with the switch in the PUBLIC position is made when the shop's owner sells the tokens for a premium above the regular price charged at the service stations of the operating companies and, therefore, also above the value stated in the telephone bill.

Notwithstanding possible advantages, the STP concept has not brought the return expected by the operating companies due to the following problems:

• The owner of the shop does not place the STP in a spot accessible to the public. Considering that the access to the exchange is made through one single telephone line, the owner fears that his line might be busy with

"public" calls that prevent him from receiving calls and doing business;

• the TPS is subject to frauds. It can be replaced by a conventional telephone and the signaling with the semi-public repeater of the exchange can be emulated by manipulating the hook; • the existing STP's use metal tokens; however, many users prefer card telephones;

• the STP's are almost exclusively installed indoors and so its use is restricted to the shop's working hours; • the STP is connected to a semi-public repeater in the exchange that has a high cost and limited number of accesses;

The purpose of the present invention is to provide a semi-public telephone with more flexibility of use, togetiier with reliability against attempted frauds. Another objective is to allow the use of cards brought in by the users without causing losses to the STP owner.

The invention fulfills the above mentioned aims, as well as others, by means of digital multiplexation of two independent telephone channels and their transmission by a line composed by a single metal wire pair. The first telephone set is directly connected to the line, and is equipped with demultiplexers which permit separation of the received signal in a first and a second channels, forwarding said second channel to a second telephone set by means of an analog interface. According to another feature of the invention, each telephone set has a separate dialling number. This permits simultaneous use of both telephones and eliminates the SUBSCRIBER / PUBLIC switch.

According to another feature of the invention, said first set is a semi- public digital telephone (STP-D) operated with a card or token, and the second set is a conventional subscriber telephone.

According to yet another feature of the invention, calls made through the conventional telephones are sent to a subscriber access in the telephone exchange. Calls made through the semi-public digital telephone (SPDT) are billed by collecting credits from the card (or token) and are not included in the subscriber's bill.

The present invention will now be described with reference to specific embodiments, taken as examples and not in a limiting sense, and from the related figures in which similar reference numbers identify similar parts:

Figure 1 illustrates a system comprising a conventional telephone and a semi-public set connected to the exchange by a single wire pair through a terminal unit integrated to the subscribers' line multiplier module, according to the principles of the invention.

Figure 2 illustrates a system in which the conventional telephone set is replaced by a public telephone according to the principles of the invention. Figure 3 illustrates the functional units composing the semi-public digital telephone (SPDT) by means of a block diagram, according to the principles of the invention. Figure 4 illustrates a system similar to that of figure 1, in which the connection between the terminal unit and the telephone switch is made by means of PCM standard circuits instead of analog accesses.

Figure 5 illustrates a system in which the exchange is the digital ISDN- type. This facilitates direct connection of the wire pair without need of additional adaptors at the terminal unit.

Referring now to the drawing in figure 1, the proposed system comprises a first semi-public telephone set 10 provided with an analog interface which allows connection of a second conventional subscriber telephone 20 through an a/b line 11. Said first set 10 is linked to the exchange through a pair of metal wires 12 connected to an exchange terminal unit (ETU) 31 in the central telephone exchange 30. Together with a plurality of similar units, this ETU is part of a subscriber line multiplying equipment (SLME) 32 that is connected to the switched public telephone network 35. Figure 1 shows the ETU 31 separated from SLME 32 only to provide a better view of the input and output of this unit.

According to the principles of the invention, the signal traveling in line 12 uses the basic format 2B + D (2 x 64k bits + 16k bits) and line code 2B1Q; the transmission speed is equal to 160k-bits/sec. Each of the ETU 31 units which make up the multiplying equipment 32 exchanges information with a set of "STP + subscriber" telephones (similar to the set of telephones 10 and 20 in the figure) through a line 12 connected to its outer access; the inner connection comprises two independent analog lines 33 and 34; the first corresponds to the semi-public STP 10 voice channel and the second one to subscriber telephone 20 voice channel. Toll collection of calls made through the semi-public telephone 10 is made by subtracting credits from the card, and the calls through the subscriber's access are included in the subscriber's bill as usual.

With the proposed system it is also possible to replace the common subscriber telephone with a public telephone (TP) 21 operated by token or card, as illustrated in figure 2. In this case a second access line 34' to the TP should be provided in the exchange, instead of the subscriber's access. In this set-up, the public telephone 21 can be of the conventional type, which is stronger and more suitable for outdoor installation.

Figure 3 shows the proposed system detail, emphasizing the blocks which are part of the semi-public set 10, according to the following description:

• Line interface, block 41, communicates with the telephone exchange through the metal wire pair 12, in which a digital signal travels at 160k-bits/sec with 2B+D format (two 64k-bit channels + 16k bits signaling) in line code 2B1Q. This interface demultiplexes the two voice channels B ₍ and B₂ (coded in 64k bit PCM) which are transmitted serially through lines 43 and 47 to blocks 42 and 46. The signaling information D in 16k bit PCM is transmitted separately to the digital interface control 44 through serial line 45 together with channel C, comprising internal operational commands and information related to the operation of the line interface.

• Digital interface control, block 44, turns serial data from channels C and D into parallel format compatible with bus 48 and vice-versa, so that the processor 55 has access to channels C and D. The latter contains the signaling information which travels in the structure of HDLC frames.

• Processor, block 55, comprising microprocessor, dynamic and static memories and control records. Its basic function is to manage all the other blocks and their respective functions. • Audio/Modem interface, Block 42, converts the 64k-bit sec PCM signal from line 43 into a voice frequency signal to the handset 13 of the semi- public telephone and vice-versa. Furthermore, it has a Modem to send statistical operational data or operating abnormality informations to the exchange. Block 55 controls this interface and manages the information reported by it, such as: off -hook handset, Modem in operation, etc.

• Subscriber Analog Interface, block 46 converts A D and D/A between line 47 and the telephone set 20, as well as communicating to the processor, through bus 48 about some conditions: handset on- or off-hook, dialing in progress, ringing current, etc. This interface also makes the aforesaid conversions in case there is a public telephone 21 instead of a conventional telephone 20, as illustrated in figure 2. In this case, it also sends the credit collecting signals to the public telephone set.

• Keyboard, display and card reader, blocks 49, 51, 52 comprising the man/machine interface in the digital semi-public telephone. • Timer, block 53, supplies the real time clock for equipment. It also comprises means to keep the day and time updated in case there is a temporary power failure.

• Power Supply, block 54, supplies power to all active circuits of the set.

Although the invention has been described based on specific embodiments, it is understood that several modifications are possible without straying away from the scope of the invention. The preceding description has an illustrative character, not a limiting one. Therefore, for example, the ETU access 31 to the switched public telephone network can be made, as shown in figure 4, through a single line 36, in which travels a standard PCM 2048k-bit signal. In this case, two channels of the PCM frame will be assigned to the information to and from sets 10 and 20 (see figure 1-b).

In the case of ISDN exchanges, the line multiplier 32 can be eliminated and line 12 may be directly connected to said exchange 37, as seen in figure 5.

Claims

1. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC TELEPHONES characterized by digital multiplexation of a first and a second independent telephone channels and transmission by a line (12) composed of a single pair of wires and ending in a first telephone set (10) equipped with demultiplexing means (41) which separate the second channel and send it to a second telephone set (20, 21).

2. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC TELEPHONES according to Claim 1, characterized by the fact that the telephone access numbers of the first and second said sets are different.

3. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC TELEPHONES according to Claim 1 , characterized by the fact that said first set (10) is a card-operated telephone.

4. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC TELEPHONES according to Claim 1, characterized by the fact that the second set (20) is a conventional subscriber telephone.

5. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC TELEPHONES according to Claim 1, characterized by the fact that the second set (21) is a public telephone, operated by cards or metal tokens.

6. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC

TELEPHONES according to Claim 1 , characterized by the fact that the transmission line (12) is connected, on the side of the exchange (30) by an exchange terminal unit (31 ) incorporated to a subscriber line multiplying equipment ( 32).

7. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC

TELEPHONES according to Claim 6, characterized by the fact that both channels traveling in a digital multiplexed frame structure at the rate of 160k- bits/sec through the subscriber line are demultiplexed in the line multiplying equipment, and thus they access two analog interfaces (33, 34), the first corresponding to a public telephone and the second one to a conventional subscriber telephone.

8. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC

TELEPHONES according to Claim 6, characterized by the fact that both channels traveling in a digital multiplexed frame structure at the rate of 160k- bits/sec through the subscriber line are demultiplexed in the line multiplying equipment, and are entered in time windows of a PCM channel (36) for transmission to the switched public network.

9. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC

TELEPHONES according to Claim 6, characterized by the fact that both channels traveling in a digital multiplexed fram structure at the rate of 160k- bits/sec through the subscriber line are connected to one RDSI access.

10. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC

TELEPHONES according to Claims 1, 2, or 4, characterized by the fact that calls coming from the conventional subscriber apparatus ( 20) are billed at the exchange for inclusion in the referred subscriber's bill.

11. IMPROVEMENT INTRODUCED IN SEMI-PUBLIC TELEPHONES according to Claims 1, 2, 3 or 4, characterized by the fact that calls coming from the card or metal token operated apparatus ( 10, 21) are billed by means of credit charging commands issued by the central switching exchange.