JP2810835B2 - Mobile public telephone equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile public telephone system mounted on a mobile body such as a train, and more particularly, to a telephone exchange connected to a general subscriber's telephone through a two-system communication network. The present invention relates to a connected mobile public telephone device.

[0002]

2. Description of the Related Art In recent years, public telephones have been installed in vehicles, ships, aircraft, trains, and the like as part of improving services for passengers in various types of transportation. In a public telephone mounted on such a mobile body, a small transceiver connected to the public telephone is mounted on the mobile body in addition to the public telephone. Then, a line is connected between the transceiver and the ground station by, for example, wireless communication. An exchange of a telephone station to which a ground station and a general subscriber telephone are connected is connected by a dedicated line.

FIG. 8 is a schematic diagram showing a car telephone system. An automobile 1 is equipped with an automobile telephone terminal 2 and an automobile telephone transceiver 3, and the automobile telephone transceiver 3 is connected to a radio telephone ground station 4 provided for each area on the ground via a radio line. A telephone exchange 5 is connected to the radio telephone ground station 4.

In such a car telephone system, since the distance between the car 1 and the radio ground station 4 is long and fluctuates as the car runs, line connection except for voice signals, line cutoff, billing signal, etc. Is converted to a digital control signal and transmitted / received. Therefore, the mobile telephone transceiver 3 sends an analog voice signal and a digital control signal to the mobile telephone terminal 2. The vehicle terminal 2 operates with a digital control signal. As described above, in the car telephone system, various information is transmitted in a four-wire system.

FIGS. 9A and 9B are schematic diagrams showing a train telephone system. As shown in FIG. 9A, an antenna 8 is laid along a track 7 on which a train 6 runs. As shown in FIG. 9 (b), a train telephone terminal 9 and a train telephone transceiver 10 are mounted in the train 6, and the train telephone transceiver 10 and a train telephone ground disposed at a train monitoring center, for example. It is connected to the station 11 via the antenna 8. The telephone exchange 5 is connected to the train telephone ground station 11.

[0006] In such a train telephone system,
Since the train telephone transceiver 10 and the antenna 8 of the train telephone ground station 11 are very close, the train telephone transceiver 10
The communication between the mobile phone and the train telephone ground station 11 is also performed by analog signals, including voice signals and control signals. Therefore, the train telephone transceiver 10 transmits a billing signal or the like to the train telephone terminal 9 by using a change in the polarity of the line current flowing through the signal line of the audio signal, as in the case of a normal public telephone. The train telephone terminal 9 operates with an analog control signal reproduced from a change in the polarity of the line current or the like. Thus, in the train telephone system, various information is transmitted in a two-wire system.

[0007]

However, as shown in FIG. 10, the above-mentioned antenna 8 is generally laid only along a trunk line 7a having a relatively large number of trains, and branches off from the trunk line 7a. In many cases, it is not laid on the branch line 7a.

[0008] Therefore, in the train 6 operated through the trunk line 7a and the branch line 7b, the train telephone terminal 9 can be used only during the period when the train 6 is traveling in the section of the trunk line 7a. As a result, the service for passengers is reduced.

In order to eliminate such inconveniences, two public telephones, a train telephone terminal 9 shown in FIG. 9 and an automobile telephone terminal 2 shown in FIG. The mobile phone terminal 2 may be used at times. In the section of the trunk line 7a where the train 6 runs at a high speed over a long distance where there are many tunnels and railway bridges, the train telephone system using the train telephone terminal 9 has a higher quality telephone than the car telephone system. Can provide service.

However, installing two public telephones, which always use only one of them, in a train has a problem that a narrow interior of the vehicle cannot be used effectively. It is uneconomical to install two public telephones.

[0011] Further, the passenger is forced to select a public telephone to be used according to the traveling section, and there is a concern that a passenger who does not know the situation may be confused.

The present invention has been made in view of such circumstances, and can switch and connect a single public telephone between a mobile telephone system using an analog line and a wireless telephone system using a digital line. It is an object of the present invention to provide a mobile public telephone device which is easy to use for a telephone user, can effectively use a narrow mobile body for a telephone installer, and can reduce the manufacturing cost as compared with a case where two telephones are installed.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a mobile public telephone apparatus according to the present invention comprises a public telephone which is mounted on a mobile body and operates by a digital control signal input from the outside, and a mobile telephone. An analog transceiver that is mounted and forms an analog line with the mobile telephone ground station via an antenna laid along the moving path of the mobile body, and a radio telephone ground mounted on the mobile body and wirelessly A digital transceiver that forms a digital line with a station, an audio signal switching unit that switches an audio signal for a public telephone between an analog transceiver and a digital transceiver, and an audio signal output from the analog transceiver A signal conversion unit that detects various control signals including a billing signal from a state of a line current flowing through the line and outputs the signal as a digital control signal, and inputs the signal to a public telephone. A control signal switching unit that switches a digital control signal between a digital control signal output from a signal conversion unit and a digital control signal output from a digital transceiver, and a moving object invading a moving path on which an antenna is not laid A switching unit for switching each switching unit to the digital transceiver.

According to another aspect of the present invention, there is provided a mobile public telephone apparatus connected to each ground station and a destination telephone terminal via a telephone line in addition to the above-described means. And a telephone station for switching the line during the call to the destination via the ground station based on the switching information of the transceiver received via the telephone.

[0015]

In the mobile public telephone apparatus thus constructed, a public telephone operated by a digital control signal in the mobile body, an analog transceiver corresponding to a train telephone transceiver of a train telephone system, for example, a car telephone A digital transceiver corresponding to the car phone transceiver of the system is mounted.

A moving object such as a train is shown in FIG.
In the period during which the vehicle is traveling on a moving path such as a branch line where no antenna is installed, both the audio signal switching unit and the control signal switching unit are connected to the digital transceiver side by the line switching control unit. In this case, since a digital control signal and a voice signal output from the digital transceiver are input to the public telephone, a communication line is formed with the wireless telephone ground station.

Further, during a period when the moving body is traveling on a moving route such as a trunk line on which an antenna is laid, each switching unit is connected to the analog transceiver. In this case, the signal converter detects a control signal including a billing signal from the state of the line current flowing through the signal line of the audio signal output from the analog transceiver, converts the control signal into a digital control signal, and sends the digital control signal to the public telephone. Therefore, since the digital control signal from the signal converter and the audio signal output from the analog transceiver are input to the public telephone, a communication line is formed with the mobile telephone ground station.

Further, in another invention, when a moving body such as a train passes a boundary between a trunk section where an antenna is laid and a branch section where an antenna is not laid during a call, line switching control is performed. Unit automatically switches each switching unit mounted on the mobile body, and automatically switches the busy line formed with the destination telephone terminal by the telephone station via the destination ground station. Can be As a result, even if the mobile object passes through the boundary, the call is not interrupted halfway.

[0019]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a mobile public telephone device according to an embodiment. The mobile public telephone apparatus of this embodiment is mounted on a train 6 running on a track 7 shown in FIG. The train 6 equipped with the mobile public telephone system is operated through a trunk line 7a and a branch line 7b shown in FIG. An antenna 8 connected to a train telephone ground station 11 is laid along the trunk line 7a. A station 12 is provided at a branch point of the branch line 7b.

In FIG. 1, an analog transceiver 13 mounted on a train is connected to a train telephone ground station 11 as a mobile telephone ground station shown in FIG. 9 via an antenna 8 disposed along a route 7. Form an analog line. The analog transceiver 13 and the public telephone 14 are connected to the audio signal switching unit 1.
5 are connected by a pair of signal lines 16a and 16b via the normally closed terminals of the changeover switches 15a and 15b.
A line current i flows through the signal lines 16a and 16b through which the audio signal a1 is transmitted between the analog transceiver 13 and the public telephone 14, similarly to a general terrestrial public telephone line.

The signal line 16 of the analog transceiver 13
a and 16b are connected to the signal conversion unit 17. The signal conversion unit 17 is provided with a line current i flowing through the signal lines 16a and 16b.
In this state, a 2-bit digital control signal b1 for controlling the operation of the public telephone 14 is detected and sent to the public telephone 14 via the data line 18 composed of two signal lines and the control signal switching section 19.

The train is equipped with a digital transceiver 20 in addition to the analog transceiver 13. The digital transceiver 20 forms a digital line with the terrestrial radio telephone ground station 4 shown in FIG. The digital transceiver 20 and the public telephone 14 are connected by a pair of signal lines 21a and 21b via the normally open terminals of the switches 15a and 15b in the audio signal switching unit 15. An analog audio signal a2 flows through a pair of signal lines 21a and 21b connecting the digital transceiver 20 and the public telephone 14.

The digital transceiver 20 is a 2-bit digital control signal b2 for controlling the operation of the public telephone 14.
Is transmitted to the public telephone 14 via the data line 22 composed of two signal lines and the control signal switching unit 19. The digital control signal b2 is transmitted to the line release g1, the line connection g2.
And a charging command g3.

When the line switching control unit 23 confirms that the train 6 has entered the branch line 7b from the main line 7a at the station 12 by a signal from the station, the line switching control unit 23 and the control signal switching unit 19 change the digital transceiver 20. A switching signal c for switching to the side is output. Conversely, when it is confirmed by the signal from the station 12 that the train 6 has entered the trunk line 7a from the line of sight 7b, a switching signal c for switching the switching units 15, 17 to the analog transceiver 13 is output.

The public telephone 14 has the same configuration as a digital telephone terminal used in a normal car telephone system. The analog audio signal a input via the audio signal switching unit 15 is input via a switch circuit 24 and a hook switch 25 to an analog circuit 26 such as a communication circuit or a PB signal generation circuit. A handset 27 is connected to the analog circuit 26.

A digital control unit 28 composed of, for example, a microcomputer is housed in the public telephone 14. The digital control unit 28 is a keyboard 2
9 drives the PB signal generation circuit in the analog circuit 26 based on the destination telephone number inputted from 9 and controls the opening and closing of the switch circuit 24 based on the digital control signal b inputted from the control signal switching section 19, An instruction to subtract the remaining card number of the inserted prepaid card is sent to the unit 30.

Next, the configuration and operation of the signal converter 17 will be described.

In the signal conversion section 17, as shown in FIG. 2, for a pair of signal lines 16a and 16b, a light emitting diode and a phototransistor for detecting the direction of a line current i flowing through the signal lines 16a and 16b. Are connected to opposite polarities. As shown in FIG.
a is a detection signal d obtained by detecting the line current i flowing in the forward direction.
1 and the other photocoupler 17b detects the line current i flowing in the reverse direction and outputs a detection signal d2. Detection signal d output from each photocoupler 17a, 17b
1 and d2 are input to an arithmetic processing unit 17c composed of, for example, a microcomputer. The arithmetic processing unit 17c determines a combination state of the detection signals d1 and d2 and outputs a digital control signal b1.

Generally, as shown in FIG. 3, the line current i supplied from the station to the public telephone has a current value of 0 in a state C in which the line is cut off, and a state A in a normal call state. It flows in the forward direction shown by. And
At the time of the billing signal, the signal flows in the opposite direction shown in state B.
Therefore, the arithmetic processing unit 17c detects the A state when the detection signal d1 is at the high (H) level state, detects the B state when the detection signal d2 is at the high (H) level state, and detects both the detection signals d1 and d2. State C is detected in a low (L) level state.

It should be noted that the duration T2 of the billing signal in the case of collecting a call fee in units of 100 yen for international calls and the like is the duration T1 of the billing signal in the case of collecting the call fee in units of 10 yen for domestic calls and the like. It is set longer than that. Therefore, it is determined for which amount of the charging signal the duration T of the charging signal, that is, the duration T of the state B.

The arithmetic processing unit 17c generates various digital control signals b1 according to the flowcharts shown in FIGS.

The time interruption process of FIG. 4 is executed each time a very short time ΔT such as one second elapses. When the flowchart is started, at P1 and P2, each detection signal d1. d
Read the signal level of 2. Both detection signals d1. If both d2 are at the L level, the state is C, and if the flag C has already been set to 1 at P3, the line is currently in the cutoff state, and the flow chart ends.

If the flag C has not been set to 1 at P3, the flag C is set to 1 and the state of the flag A is checked (P4). When the flag A is 1, since the state has changed from the state A to the state C, the digital control signal b of the line release g1
Outputs 1. Then, the flag A is reset to 0.

P1. In P2, when the detection signal d1 is at the L level and the detection signal d2 is at the H level, the state is B, so the flag B is set to 1 and the state of the flag A is checked (P5). When the flag A is 1, since the state A has changed from the state A to the state B for the first time, the flag A is reset to 0, the duration T of the billing signal is reset to 0, and the measurement of the duration T is started. If the flag A is already 0 (P
5) Add the small time ΔT to the duration T during the measurement (T = T + ΔT).

At P1 in FIG. 4 and P6 in FIG. 5, when the detection signal d1 is at the H level and the detection signal d2 is at the L level, the state is A, so the state of the flag A is checked (P
7). If it has already been set to 1, the flow chart is ended without doing anything because a normal call is in progress. Flag A
Is still released to 0 (P7), since it has changed to the state A for the first time this time, the flag A is set to 1 and the state before the change to the state A is examined.

That is, if the flag B has been cleared to 0 (P8) and the flag C has been set to 1, (P
9) Since the state has shifted from the state C to the state A, the line connection g2
Is transmitted.

If the flag B is set to 1 (P8), the charging signal ends and the state B is shifted to the state A, so that the continuation time T of the charging signal is checked in P10 and P11. When the continuation time T is the time T1 corresponding to 10 yen in P10, the digital control signal b1 indicating the charge command g3 of 10 yen is transmitted. Also, if the duration time T is P
In case of time T2 corresponding to 100 yen in 11
A digital control signal b1 indicating a charge command g3 of 0 yen is transmitted. Thereafter, the flag B is reset to 0.

In the case of the mobile public telephone having the above configuration, when the train 6 is running on the branch line 7b, the audio signal switching unit 1 is controlled by the line switching control unit 23.
5 and the control signal switching unit 19 are both digital transceivers 20.
Connected to the side. Therefore, the public telephone 14 is connected to the digital transceiver 20.

In this state, when the passenger picks up the handset 27 from the public telephone 14, inserts the prepayment card into the billing unit 30 and inputs the telephone number of the destination with the keyboard 29, the signal is transmitted through the signal lines 21 a and 21 b. The PB signal is transmitted to the digital transceiver 20, and the digital transceiver 2
At 0, it is converted to a digital signal and transmitted to the radio telephone ground station 4. Then, a call signal is transmitted from the radio telephone ground station 4 to the telephone terminal of the call destination via the exchange 5 of the telephone station. When the handset of the called telephone terminal is picked up, a communication line is formed between the public telephone 14 of the train and the called telephone end.

When the communication line is established, various digital control signals b2 including the charging command g3 are transmitted from the radio telephone ground station 4 to the digital transceiver 20. The digital transceiver 20 transmits the received digital control signal b2 to the digital control unit 28 of the public telephone 14 via the control signal switching unit 19 as it is. Therefore, the public telephone 14 operates normally according to the digital control signal b2.

Next, the train 6 is connected to the branch line 7b via the station 12.
, The line switching control unit 23 operates to switch and connect the switching units 15 and 19 to the analog transceiver 13 side. In this state, the public telephone 14 is connected to the analog transceiver 13.

As described above, when the passenger performs a calling operation on the public telephone 14, the signal lines 16a, 16b
PB signal is sent to the analog transceiver 13 via
The signal is transmitted from the analog transceiver 13 to the train telephone ground station 11 via the antenna 8. Then, a call signal is transmitted from the train telephone ground station 11 to the telephone terminal of the call destination via the exchange 5 of the telephone station, and the handset of the telephone terminal of the call destination is picked up. A telephone line is formed between the telephone terminal and the telephone terminal.

When a communication line is formed, various control signals including an analog billing signal are transmitted from the train telephone ground station 4 while being superimposed on the analog communication signal. The analog transceiver 13 transmits the received control signal to the signal line 16a of the call signal.
The signal line 1 changes as the state change of the line current i flowing through the line 16b.
6a and 16b.

As shown in FIG. 3, the signal conversion unit 17 outputs the state A. of the line current i. A change in B and C is detected, and this change is converted into a digital control signal b1 for line connection, line cutoff, charge command, etc., and transmitted to the digital control unit 18 of the public telephone 14. Therefore, the public telephone 14 operates normally according to the digital control signal b1.

As described above, the traveling section of the train 6 is
Regardless of the branch line 7b, the passenger can call the general subscriber telephone on the ground with the same public telephone 14 and the same operation to carry out a telephone call. Therefore, unlike the conventional apparatus, the passenger is not forced to select a public telephone that can be used in the traveling section, so that a good telephone service for the passenger can be provided.

Further, as compared with the conventional system in which it is necessary to install two public telephones each having a different telephone system, the number of public telephones can be reduced to one without lowering the telephone service. Significant cost savings.

Further, since there is no need to install two public telephones which can be used at all times, a narrow train space can be effectively used.

FIG. 6 is a block diagram showing a schematic configuration of a mobile public telephone apparatus according to another embodiment of the present invention. In the train 6 operated through the main line 7a and the branch line 7b, main units such as the public telephone 14, the analog transceiver 13, the digital transceiver 20, and the line switching control unit 23 shown in FIG.

A train telephone ground station 11 is connected to an antenna 8 arranged along the trunk line 7a, and a radio telephone ground station 4 covering a wide area including a branch line where the antenna 8 is not laid is installed. ing. Train telephone ground station 1
1 and the radio telephone ground station 4 are connected to a telephone station 31 via a communication line.
It is connected to the.

The telephone station 31 is connected via a telephone network 32 to another telephone station 34 to which a called telephone terminal 33 is connected.

In this embodiment, when the train 6 passes the station 12 and the public telephone 14 mounted on the train 6 is communicating with the telephone terminal 32 on the ground, the telephone office 31 It has the function of switching the middle line to the destination ground station.

The specific operation will be described with reference to the sequence diagram shown in FIG.

First, when the caller performs a dial operation on the public telephone 14 while the train 6 is traveling on the trunk line 7a, the talker terminal 3 is called to the telephone station 31 via the train telephone ground station 11.
A telephone number of 3 is sent. The telephone station 31 stores the number of the public telephone 14 of the train 6 from which the call originated, calls the destination telephone terminal 33 via the telephone office 34, and sets the train between the public telephone 14 and the telephone terminal 33. A communication line is formed via the telephone ground station 11.

When the train 6 arrives at the station 12 in a call state,
As described above, the switching signal c is transmitted from the line switching control unit 23, and the public telephone 14 is switched and connected to the digital transceiver 20 side. The analog transceiver 13 detects the switching operation and transmits the switching information to the telephone station 3 via the train telephone ground station 11.
Send to 1. Upon receiving this switching information, the telephone station 31 uses the stored telephone number of the calling public telephone 14 via the wireless telephone ground station 4 to transmit the public telephone 1 of the train 6.
Then, the calling line of the destination telephone terminal 33 is switched from via the train telephone ground station 11 to via the wireless telephone ground station 4.

Conversely, when the caller dials the public telephone 14 while the train 6 is running on the branch line 7b, the talker terminal 3 is called to the telephone station 31 via the wireless car telephone ground station 4.
A telephone number of 3 is sent. The telephone station 31 stores the number of the calling public telephone 14, calls the called telephone terminal 33 via the telephone office 34, and places the train telephone ground station 11 between the public telephone 14 and the telephone terminal 33. Form a telephone line via

When the train 6 arrives at the station 12 in a call state,
As described above, the switching signal c is sent from the line switching controller 23, and the public telephone 14 is switched and connected to the analog transceiver 13 side. The digital transceiver 20 detects the switching operation and transmits the switching information via the radio telephone ground station 4 to the telephone station 31.
Send to Upon receiving this switching information, the telephone station 31 calls the public telephone 14 of the train 6 via the train telephone ground station 11 with the stored telephone number of the public telephone 14 of the calling source, and The 33 busy lines are switched from via the wireless ground station 4 to via the train ground station 11.

With the mobile public telephone apparatus configured as described above, when the public telephone 14 mounted on the train 6 is communicating with the destination telephone terminal 32 on the ground when the train 6 passes through the station 12, The public telephone 14 is switched and connected to the transceivers 13 and 20 on the side corresponding to the side on which the train 6 travels, and the ground line 11 is also connected to the ground station 11 on the side corresponding to the side on which the train 6 advances. , 4 are switched.

Therefore, even if the train 6 passes the switching station 12, it is possible to continue the call as it is. Therefore, the service for the user of the public telephone 14 can be further improved.

[0060]

As described above, according to the train public telephone system of the present invention, the change of the state of the two-wire type line current is converted into a digital control signal by the signal conversion unit, whereby 1
The public telephones are switched and connected to a train telephone system using an analog line or a wireless telephone system using a digital line. Therefore, it is easy for passengers to use, and the telephone installer can effectively use the inside of the narrow train, and the manufacturing cost can be significantly reduced as compared with the case where two trains are installed.

Further, even if the communication system is changed during a call, the call can be continued without interrupting the call, and the service for the user can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a train public telephone device according to one embodiment of the present invention.

FIG. 2 is a circuit diagram of a signal converter in the device of the embodiment.

FIG. 3 is a time chart showing the operation of the signal conversion unit.

FIG. 4 is a flowchart showing the operation of the signal conversion unit.

FIG. 5 is a flowchart showing the operation of the signal conversion unit.

FIG. 6 is a schematic diagram showing a schematic configuration of a train public telephone device according to another embodiment of the present invention.

FIG. 7 is a sequence diagram showing the operation of the apparatus of the embodiment.

FIG. 8 is a schematic view showing a general car telephone system.

FIG. 9 is a schematic diagram showing a general train telephone system.

FIG. 10 is a diagram showing a main line and branch lines on which a train operates.

[Explanation of symbols]

Reference numeral 4: radio telephone ground station, 5: exchange, 6: train, 7: track, 7a: trunk line. 7b: branch line, 8: antenna, 11: train telephone ground station, 13: analog transceiver, 14: public telephone, 15: voice signal switching unit, 16a, 16b, 21
a, 21b: signal line, 17: signal conversion unit, 19: control signal switching unit, 20: digital transceiver, 23: line switching control unit, 31: telephone office, 33: destination telephone terminal.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuneo Yajima 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Satoshi Hoshi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (58) Fields surveyed (Int.Cl. ⁶ , DB name) H04B 7/24-7/26 H04Q 7/00-7/38

Claims (2)

(57) [Claims] 1. A public telephone (14) mounted on a moving body and operated by a digital control signal input from the outside, and an antenna mounted on the moving body and laid along a moving path of the moving body. (13) an analog transceiver for forming an analog line with the mobile telephone ground station, and a digital transceiver mounted on the mobile body and forming a digital line with the wireless telephone ground station via radio (20), an audio signal switching unit (15) for switching an audio signal for the public telephone between the analog transceiver and the digital transceiver, and a line flowing through a signal line of an audio signal output from the analog transceiver. From the state of the current, a signal conversion unit (17) that detects various control signals including a billing signal and outputs it as a digital control signal, and a digital control signal input to the public telephone from the signal conversion unit. A control signal switching unit (19) for switching between a digital control signal to be input and a digital control signal output from the digital transceiver, and when the moving object enters a moving path on which the antenna is not laid, A mobile public telephone device comprising a line switching control unit (23) for switching each switching unit to a digital transceiver. 2. A public telephone (14) mounted on a moving body and operated by a digital control signal input from the outside, and an antenna mounted on the moving body and laid along a moving path of the moving body. (13) an analog transceiver for forming an analog line with the mobile telephone ground station, and a digital transceiver mounted on the mobile body and forming a digital line with the wireless telephone ground station via radio (20), an audio signal switching unit (15) for switching an audio signal for the public telephone between the analog transceiver and the digital transceiver, and a line flowing through a signal line of an audio signal output from the analog transceiver. From the state of the current, a signal conversion unit (17) that detects various control signals including a billing signal and outputs it as a digital control signal, and a digital control signal input to the public telephone from the signal conversion unit. A control signal switching unit (19) for switching between a digital control signal to be input and a digital control signal output from the digital transceiver, and when the moving object enters a moving path on which the antenna is not laid, A line switching control unit (23) for switching each switching unit to the digital transceiver side, connected to each of the ground stations and the called telephone terminal via a telephone line, and received via the analog transceiver or the digital transceiver. A mobile public telephone device comprising: a telephone station (31) for switching a busy line to a destination via a ground station based on switching information of the transceiver.