Radio channel control system for mobile radio telephone systems

In a mobile telephone system of the type in which the service area of the system is divided into a plurality of radio zones, mobile-system base stations are installed in respective radio zones, each mobile-system base station is connected to a mobile-system control unit through a common control channel and a plurality of speech channels, and the mobile-system control unit is connected to an existing telephone network via a mobile-system exchange unit, there are provided signal lines extending between the mobile-system base stations and the mobile-system control unit and between the mobile-system control unit and the mobile-system exchange unit and respectively combined with each of the speech channels. These signal lines are used to determine the state of the speech channels, and to transmit control and information signals.

BACKGROUND OF THE INVENTION 
This invention relates to a system of controlling radio channels of a 
mobile radio telephone system. 
With increased activity of human living, the requirements for communicating 
between vehicles such as motor cars, ships, trains, etc. by utilizing 
existing ordinary telephone networks, have been increasing and various 
mobile radio telephone systems have been developed to fulfil such 
requirements. 
Among these systems, a system is now being used wherein a service area of 
the system is divided into a plurality of radio zones, a mobile-system 
base station (MBS) is installed in each radio zone, and the mobile-system 
base stations are connected to a mobile-system control unit (MCU) through 
a common control channel and speech channels each consisting of four lines 
whereby the mobile-system base stations are connected to an ordinary 
telephone network through the mobile-system control unit. Such a system is 
described in U.S. Pat. No. 3,663,762 dated May 16, 1972 and Z. C. Fluhr 
and E. Nussbaum paper of the title "Switching Plan for a Collular Mobile 
Telephone System" I.E.E.E. Transaction on Communications, Vol. COM-21, 
Nov. 1973. The reason for using a common control channel in this system is 
to improve the control efficiency and the efficiency of utilization of the 
speech channels by commonly controlling a plurality of speech channels at 
a high speed where a mobile communication service is contemplated in a 
high capacity and over a wide area. 
However, the prior art system is accompanied by a number of problems so 
that its reliability is not yet sufficiently high as will be described 
hereunder. 
More particularly, the mobile-system base stations, the mobile-system 
control unit and the mobile-system exchange unit are interconnected by a 
four line speech channels and a control channel common to respective 
speech channels, and the information for controlling the processing of 
origination and paging are transmitted through a common control line or 
channel. Moreover, the information transmitted through the common control 
line is in the form of digital information. Although digital information 
is efficient for high speed and high density transmissions it is liable to 
be affected by noise. For this reason, where digital information is used, 
it is usual to use an expensive and complicated check circuit in order to 
assure extremely high accuracies. The use of such check circuit, however 
results in the complication of the system control and in the increase in 
the cost of installation. Furthermore, where the information regarding the 
state of the radio channel of each speech channel is to be transmitted 
continuously, sending this information over a common control channel may 
be difficult due to the large volume of information which must be sent to 
represent the constantly changing state of the radio channel. 
In addition, since the radio telephone system utilizes wireless waves as 
the information transmission medium, it involves various problems specific 
to radio transmission. Firstly, due to decrease in the transmission 
characteristics caused by fading phenomena control information sent to or 
received from mobile vehicles will not be transmitted accurately, or when 
a speech channel is available between a mobile vehicle and a mobile-system 
base station it will be difficult to maintain desired speech quality. In 
addition, under these conditions, an electric wave utilized in another 
radio zone may enter into an idle speech channel or may cause interference 
with waves of the adjacent zones. 
The state of the radio channel for each speech channel is represented by 
the presence of an electric wave which indicates whether the channel is 
available or not, and the mobile-system base stations, mobile-system 
control unit and mobile-system exchange unit are required to acknowledge 
such information. In view of the large volume of information required to 
represent the constantly changing state of the speech channels, however, 
it is impossible to transmit such information over the common control 
channel. However, the provision of control lines for transmitting digital 
signals corresponding to respective speech channels increases the size and 
cost of installation. 
Due to these problems, among various operations of the system, selection of 
an idle speech channel is most severely affected. Generally, to select an 
idle speech channel, an idle speech channel memory device (or a temporary 
memory device) adapted to store an idle or busy state of the speech 
channel is provided for finding an idle speech channel out of a plurality 
of speech channels where a request for origination or paging is made. In 
the prior art system, it is impossible to change the channel content of 
the idle speech channel memory device except a case wherein the channel 
content is changed to a blocked state for the purpose of designating a new 
channel and a case wherein the channel content is changed to idle state 
when the speech of a given channel is terminated. 
For this reason, where the channel content has been changed by an erroneous 
control data, even when the controller of the mobile-system control unit 
designates a speech channel based on the content of the idle speech 
channel memory device it may happen to designate a busy speech channel or 
to fail to designate a channel when the channel content is blocked 
irrespective of the fact that it is actually in an idle state. When an 
actually idle speech channel is designated under a poor wave transmission 
condition, it would be impossible to maintain the desired speech quality. 
Where the wave transmission condition becomes poor during speech and 
irrespective of the fact that the speech has already been terminated the 
speech channel might be continuously disabled when the mobile control unit 
fails to detect termination of the speech. Under these conditions, the 
mobile vehicle and the mobile base station continue to radiate electric 
waves. 
Another problem is that the reliability of all speech channels of a given 
mobile base station would be decreased when there is some transmission 
trouble, for example noise, wire breakage, etc., occurs on the common 
control channel. 
Still another problem is that when it becomes impossible to generate 
control digital data due to a system trouble of the radio mobile control 
unit, control of the transmitter of the mobile-system base station becomes 
completely impossible. 
SUMMARY OF THE INVENTION 
Accordingly, the principal object of this invention is to provide a novel 
control system of radio channels of a mobile radio telephone system which 
can always supervize the state of the radio speech channels thereby 
maintaining high speech qualities. 
Another object of this invention is to provide a highly reliable control 
system for radio channels of a mobile radio telephone system which does 
not select an idle speech channel if there is a wave interference in that 
channel and which can prevent radiation of useless wave from a transmitter 
associated with an idle speech channel which might otherwise cause mutual 
interference of the electric waves. 
Still another object of this invention is to provide a control system of 
radio channels of a mobile radio telephone system capable of preventing 
continuous disablement of a speech channel irrespective of the fact that 
the speech of that channel has already been terminated thereby increasing 
the reliability of the speech channels. 
A further object of this invention is to provide a control system of radio 
channels of a mobile radio telephone system capable of restoring the 
mobile-system base station to a normal operating condition when a system 
trouble occurs in the mobile-system control unit during speech. 
Still another object of this invention is to provide a control system of 
radio channels of a mobile telephone system capable of eliminating a 
mismatch condition even when the content of the speech channel memory 
device and the state of a speech channel become mismatched due to a system 
trouble such as a fault in the sequence controller. 
Yet another object of this invention is to provide a control system of the 
radio channels of a mobile radio telephone system. 
According to this invention these and further objects can be accomplished 
by providing a radio channel control system for a mobile radio telephone 
system of the type wherein the service area of the system is divided into 
a plurality of radio zones, mobile-system base stations are installed in 
respective radio zones, each mobile-system base station is connected to a 
mobile-system control unit through a control channel and a plurality of 
speech channels, and the mobile control unit is connected to an ordinary 
telephone network, wherein said radio channel control system comprises a 
plurality of signal lines extending between the mobile-system base 
stations and the mobile-system control unit and combined with respective 
speech channels. 
The signal lines are used to display the states of the speech channels or 
to transmit control informations for remotely controlling the 
mobile-system base stations. It is possible to accurately determine the 
state of the speech channel from the signals obtained by the signal lines. 
Accordingly it is possible to change the content of the idle speech 
channel memory device by these signals. 
According to another embodiment of this invention these signal lines are 
used to control transmission and termination of the electric waves from 
radio transmitters provided for respective mobile-system base stations, 
such control being effected by a signal sent from the mobile-system 
control unit. When system troubles occur in the mobile-system control 
unit, it is possible to interrupt the source of the transmitter in each 
mobile base station by using the signal line. This is advantageous where 
the mobile-system base station is automated or located at a remote 
position. 
According to another embodiment where a speech channel is busy or radiating 
an electric wave, a on signal is sent through the signal line whereas when 
the speech channel is idle that is in an available state the signal line 
is released to be off. For this reason, information transmitted through 
the signal line or relatively free from noise.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The basic construction of a mobile radio telephone system to which the 
control system of this invention is applicable will first be described. 
The Principle of the System 
In the mobile radio telephone system shown in FIG. 1, the service area of 
the system is divided into n radio zones 10.sub.l, through 10.sub.n (where 
n is an integer) and mobile-system base stations (hereinbelow sometimes 
referred to as mobile base stations) 11.sub.l through 11.sub.n are 
installed in respective radio zones. Each zone has a radius of about 5 km, 
for example. In this example the number of the radio zones is four. Speech 
channels f.sub.il -f.sub.im (where m is an integer) are assigned to the 
nth mobile base station 11.sub.i (where i=1-n). These mobile base stations 
11.sub.l -11.sub.n are commonly controlled by a mobile-system control unit 
(hereinbelow sometimes referred to as mobile control unit) 12. M 
represents a vehicle, shown in the radio zone 10.sub.l in this example. 
The basic operation of this system will be described briefly with reference 
to FIG. 1. When the vehicle M originates, it transmits an origination 
signal via a control channel F.sub.l and the radiated origination signal 
is received by all nearby mobile base stations 11.sub.l through 11.sub.n 
because the control channel F.sub.l is common to all mobile base stations. 
Each of the mobile base station adds to the received signal, a signal 
corresponding to the intensity of the received wave and then sends the 
resulting sum signal to the mobile control unit 12. This control unit 12 
is normally in a condition for waiting for the origination signal so that 
when it receives the origination signal from the vehicle it determines one 
of the mobile base stations which sends the strongest signal and then 
searches for an idle speech channel of said one station. When there is an 
idle speech channel, said one mobile base station transmits information 
regarding the idle speech channel to all other mobile base stations 
11.sub.l through 11.sub.n through the control channel F.sub.1. 
When the vehicle receives a signal regarding the designation of the idle 
speech channel the vehicle M is switched to channel f.sub.11. 
The mobile-system exchange unit (hereinbelow sometimes referred to as 
mobile exchange unit) 13 is constructed to establish a connection between 
the calling and the called party as well as a connection from the vehicle 
M through the mobile exchange unit to an ordinary telephone network in 
response to the origination from the vehicle. 
According to this invention, signal lines, (for example, one up path and 
one down path) are provided for each one of the speech channels extending 
between respective mobile base stations and the mobile control unit 12. 
The telephone system of this type is generally provided with four lines in 
each of the speech channels (two up path, two down path) and two common 
control channels, these channels constituting a basic unit, so that one 
signal line is added to each of the up and down path speech channels. In 
FIG. 2, each two up and down path speech channels are grouped and shown as 
an AB up path speech channel 14.sub.a and a DE down path speech channel 
14.sub.b whereas a BU up path signal line 15.sub.a and a BD down path 
signal line 15.sub.b are shown independently. Regarding the common control 
channel, both of the up and down path control channels are grouped and 
shown by a single thick line 16. In this example, an up path speech 
channel 17.sub.a (AB), a down path speech channel 17.sub.b (DE), an up 
path signal line 18a(CU) and a down path signal line 18.sub.b (CD) are 
also provided between the mobile control unit 12 and the mobile exchange 
unit 13. 
In this manner, by providing signal lines corresponding to respective 
speech channels and independent of the common control channel between the 
mobile base station and the mobile control unit and between the mobile 
control unit and the mobile exchange unit it becomes possible to transmit 
information representing the status of the speech channels and control 
information for remotely controlling the mobile base stations via these 
signal lines thus enabling more precise control. Since these signal lines 
correspond to respective speech channels, it is possible to manually 
control the mobile base stations when system troubles occur in the mobile 
control unit 12 or the control channel becomes out or order. As a 
consequence, it is possible to control the speech termination at the time 
of fault of the mobile control unit or the data channel thus minimizing 
the poor or adverse effect of the interference to the speech. As a 
consequence, the reliability of the system can be greatly improved. 
With this arrangement, since the signal lines represent the actual state of 
the radio speech lines, even when the content of the idle speech channel 
memory device of the mobile control unit is damaged or system troubles 
occur, it is possible to reconstruct the content in accordance with the 
state of the signal line. Accordingly, it is not necessary to install the 
idle speech channel memory device in duplicate, thus decreasing the chance 
of troubles of the speech channel control. 
The detail of each unit will be described hereunder to make clear the 
feature of this invention. 
Mobile Base Stations 11.sub.l -11.sub.n 
Since all mobile base stations have the same construction, the detail of 
the mobile base station 11.sub.l is shown in FIG. 3 as a representative. 
As shown, the mobile base station 11.sub.l is equipped with an antenna 20 
for communicating electric wave between it and the vehicle M. The antenna 
20 is connected to a speech channel transmitter 23, a speech channel 
receiver 24, a control channel transmitter 25 and a control channel 
receiver 26 respectively through a RF multiplexer 21. The speech channel 
transmitter and receiver 23 and 24 are connected, via a MBS controller 28, 
to the down path speech channel 14.sub.a (DE) and the up path speech 
channel 14.sub.b (AB) which are extending between the MBS controller and 
the mobile control unit 12. The control channel transmitter and receiver 
25 and 26 are connected via the MBS controller 28, to down and up path 
control channels 16a and 16b extending between the MBS controller 28 and 
the mobile control unit 12. The MBS controller 28 has an operational 
function which stands for a buffer and a repeater etc. 
To the output of the speech channel receiver 24 is connected an up path 
speech channel state detector 35 which detects the state of the up path 
speech channel 14.sub.a and the output of the detector 35 is connected to 
the mobile control unit 12 via the up path signal line 15.sub.a. 
To the input of the speech channel transmitter 23 is connected a down path 
speech channel controller 38 which is connected to receive, via the MBS 
controller 28, a signal from a down path signal line 15.sub.b (BD) 
connected to the mobile control unit 12, thereby controlling the operation 
of the transmitter 23 in accordance with the received signal. 
The mobile base station 11.sub.l constructed as above described, converts 
control data information received from the vehicle M into information 
suitable for the control of the mobile control unit 12 in a manner to be 
described later, or to repeat the control data information received from 
the mobile control unit 12 to the mobile vehicle. 
An example of the circuits associated with the signal lines will now be 
described with reference to FIGS. 4 and 5. 
At first, the construction of the speech channel receiver 24 and the up 
path channel state detector 35 will be described with reference to FIG. 4. 
The signal received from the antenna 20 via the RF multiplexer 21 is sent 
to a RF (radio frequency) amplifier 41 where the signal is connected into 
an IF (intermediate frequency) signal by the corporation of the high 
frequency amplifier and a local oscillator 42. The IF signal is amplified 
by an IF amplifier 43, demodulated by an demodulator 44 and finally sent 
out to the MBS controller 28. The IF amplifier 43 send a signal to a level 
detector 46 which provides an output to an integrator 47 when the level of 
the input exceeds a predetermined level. The output of the integrator 47 
is applied to first and second judging units 48 and 49. 
The first judging unit 48 produces an output when the integrator 47 
produces a continuous output for a predetermined interval T.sub.1 of the 
order of several tens milliseconds. Continuous output of the integrator 47 
means that the electric wave from the vehicle M is being continuously 
received. When the electric wave is interrupted during the speech for a 
predetermined time, it is judged that the quality of the speech has 
decreased and the speech channel is released. Furthermore, when the 
presence of electric wave is detected during a period that the speech 
channel is not in use, it is judged that there is a wave interference. 
The signal repeating operation at the time of receiving and not receiving 
electric wave is as follows. 
The output of the first judging unit 48 is applied to the set terminals S 
of a flip-flop circuit 50 to set the same. As a consequence its Q output 
is applied to a relay 51 which produces an output, for example grounded 
signal, as the output of the up path speech channel state detector 35. 
This output acting as a signal indicating that the speech channel is 
suffering a wave interference is sent to the mobile control station 12 via 
the up path signal line 15.sub.a (BU). 
The second judging unit 49 produces an output when the output of the 
integrator 47 is interrupted for a predetermined time T.sub.2 of the order 
of several seconds (T.sub.2 &gt;T.sub.1). The interruption of the output from 
the integrator 47 for a predetermined time means that the speech has 
terminated or the wave interference has disappeared. The output of the 
second judging unit 49 is applied to the reset terminal R of the flip-flop 
circuit 50 to reset the same. Then, the Q output of the flip-flop circuit 
50 disappears so that the relay 51 is deenergized. 
The reason that the set time T.sub.1 of the first judging unit 48 is made 
to be smaller than the set time T.sub.2 of the second judging unit 49 is 
that the wave presence state is to be rapidly detected with a short time 
constant whereas the wave absence state should be confirmed with a 
sufficiently long time constant to render idle the channel so as to assure 
that the on or off-operation of the up path signal line will not be 
rendered unstable due to the variation in the level of the received wave. 
Since the speech channel state detector 35 utilizes integrator 47 as above 
described, the first and second judging units 48, 49 will not operate 
immediately even when the state of the speech channel is caused to vary by 
a noise of short time. 
The output of the up path speech channel state detector 35 represents the 
state of this speech channel. When an on-signal is produced as the output, 
this speech channel is in a state difficult or impossible to operate due 
to wave interference. As a consequence, the presence and absence of the 
on-signal is used to check and confirm the present state of an idle speech 
channel selected from the idle speech channel memory device where an 
origination or paging is made in the mobile control unit 12 as will be 
described later. The on-signal is also used to periodically supervize the 
content of the idle speech channel memory device and the actual state of 
the speech channel for the purpose of preventing any mismatch between 
them. The on-signal is also used as one step of the speech termination 
operation thereby positively terminating the speech. 
One example of the speech channel transmitter 23 and the down path speech 
channel controller 38 will now be described with reference to FIG. 5. 
The voice signal sent from the radio control unit 12 via the down path 
speech channel 14.sub.b and the MBS controller 28 is applied to a 
modulator 60 of the speech channel transmitter 60. The output of the 
modulator 60 is sent to the RF multiplexer 21 via a frequency converter 
61, a frequency multiplier 62 and a RF amplifier 63 to be radiated through 
antenna 20. The frequency converter 61 converts the frequency of the 
output of the modulator 60 in accordance with the output of a local 
oscillator 64. 
The signal sent from the mobile control unit 12 via the down path signal 
line 14.sub.b is sent to a relay 66 of the MBS controller 28 of the down 
path speech channel controller 38. The signal supplied to relay 66 
normally opens it. When the mobile control unit 12 detects the origination 
from the vehicle 12, a radio zone to be used is selected in accordance 
with the content of the data. Thus, an idle speech channel of that radio 
zone is determined so as to send channel information to the mobile 
exchange unit. At the same time, an on-signal is sent to the down path 
signal line of the selected idle speech channel. When the relay 66 is 
energized by the on-signal, it turns on the source of the RF amplifier 63 
of the speech channel transmitter 23. Thereafter, the speech channel 
transmitter 23 is maintained in a state of sending its output to the RF 
multiplexer 21 by a signal sent from the mobile control unit 12 via the 
down path speech channel. 
Furthermore, the down path speech channel controller 23 turns OFF the 
source for the RF amplifier 63 of the speech channel transmitter 23 at the 
termination of the speech. This operation is effected by detecting the 
disappearance of the on-signal (for example, grounded signal) supplied to 
relay 66 during speech by a BD off detector 67. When this detector detects 
the BD-off state it drives an encoder 68 to supply a speech channel 
release signal to the modulator 60. This release signal is sent to the 
vehicle M through the speech channel transmitter 23, RF multiplexer 21 and 
antenna 20 thereby causing the vehicle M to release or open the speech 
channel. The output of the BD off detector 67 is sent to encoder 68 and a 
timer or a delay circuit 69 so that after sending the release signal to 
the mobile vehicle M for about one second, the output of the detector 67 
is sent to the RF amplifier 63 of the speech channel transmitter 23, thus 
turning off the source. Consequently, thereafter the speech channel 
transmitter 23 would not operate unless a BD on-signal is sent to the down 
path speech channel controller 38 through the down path signal line 
15.sub.b. The source on command from relay 66 and the source off command 
from timer 69 cause the RF amplifier 63 to turn on and off its bias 
source, respectively. Alternatively, the output stage of the RF amplifier 
63 is turned on or off under the same condition. 
In this manner, it is possible to decrease the mutual interference between 
the down path speech channels by shutting off the wave transmitted from a 
mobile base station by energizing the speech channel transmitter 23 only 
during the speech but deenergizing the transmitter 23 in the absence of 
the speech. 
Mobile Control Unit 12 
The basic construction of the mobile control unit 12 is shown in FIG. 6. As 
shown, speech channels 14.sub.a, 14.sub.b and signal lines 15, 15.sub.b 
connected to the mobile base station (MBS) controller 28 of the mobile 
base station 11.sub.1 are respectively connected to a speech path unit 
(SPU) 71 which forms a portion of the mobile control unit 12. The speech 
path unit 71 is connected to a mobile exchange unit 13 through speech 
channels 17.sub.a, 17.sub.b. The control channels connected to the MBS 
controller 28 of the mobile base station 11.sub.1 are connected to a 
combined encoder and decoder 74 which contains a modulator and a 
demodulator (not shown) and constitutes a portion of the mobile control 
unit 12. The combined encoder and decoder 74 is constructed to send 
control data to the mobile base station 11.sub.1 or vice versa under the 
control of a sequence controller 76. The sequence controller 76 is 
connected to a sequence memory device 77, an idle speech channel memory 
device 78 that constitutes a portion of the temporary memory device, a 
timing circuit 79, a SPU controller 80, a scanner 81 and a sense port 82 
through a data bus line 85 and an address bus line 86. Furthermore, the 
sequence controller 76 is connected to a second combined encoder and 
decoder 88 (also including a modulator and a demodulator not shown) via 
the data bus line 85 and the address bus line 86. The combined encoder and 
decoder 88 is connected to the mobile exchange unit 13 through common 
control channels 19.sub.a and 19.sub.b to exchange control data therewith. 
In addition to the idle speech channel memory device described above, the 
temporary memory device may comprise a SPU correspondence memory device 
which stores the corresponding relationship to SPU or a memory device that 
stores an information regarding the origination of a mobile vehicle, or a 
timer table memory device. However, as these memory devices are immaterial 
to this invention their detailed description will not be made herein. 
Mobile Exchange Unit 13 
The basic construction of the mobile exchange unit 13 is shown in FIG. 11. 
As shown, the mobile exchange unit 13 is connected to the mobile control 
unit 12 via four up and down path speech channels 17.sub.a and 17.sub.b, 
two up and down path signal lines 18 and 18.sub.b and two up and down path 
control lines 19.sub.a and 19.sub.b and provided with apparatus necessary 
to connect the radio telephone system with an ordinary telephone network. 
The common control lines 19.sub.a and 19.sub.b connected to the combined 
encoder and decoder 88 of the mobile control unit 12 are connected to a 
combined encoder and decoder 91 also including a modulator and 
demodulator, not shown, so as to communicate control data therebetween 
over the common control lines. The combined encoder and decoder 91 is 
connected to a sequence controller 94 via a data bus line 92 and an 
address bus line 93, and the sequence controller 94 is connected to a 
timing circuit 96, a sequence memory device 97, a station data memory 
device 98, a temporary memory device 99, and a common line signal device 
100 via the data bus line 92 and the address bus line 93. In this case, 
the temporary memory device 99 is constituted by a paging memory device, a 
busy memory device and an origination memory device, while the station 
data memory device 98 is constructed to store stored channel numbers 
corresponding to respective mobile base stations. 
The mobile exchange unit 13 further comprises a speech path switching 
network 102, a bidirectional or both way trunk 103, an incoming trunk 
(ICT) 104, an outgoing trunk (OGT) 105, a ring-back tone trunk (RBT) 106, 
an origination sender trunk (OST) 107, an incoming register trunk (IRT) 
108, a mobile loop check trunk (MLCT) 109. These trunks are connected to 
the sequence controller 94 through bus lines 92 and 93. 
The purpose of the common line signal device 100 is to communicate control 
data with an ordinary telephone network and includes a buffer memory 
device for storing control data, a memory designator that designates the 
buffer memory device based on the address information. 
The operations of the mobile control unit 12 and the mobile exchange unit 
13 at the times of origination and paging are described in detail in the 
specification of a copending U.S. Patent application Ser. No. 801,022 
filed on May 26, 1977 under of a title "Radio Channel Control Systems of 
Mobile Radio Telephone Systems". 
Origination Operations of Mobile Control Unit 12 and Mobile Exchange Unit 
13 
Normally, the sequence controller 76 is in a waiting state and operates to 
supervize whether a mobile vehicle M has originated or not, or whether a 
paging is made from an ordinary telephone network through the common 
control channel. 
When an origination signal as shown in FIG. 7A is received by the control 
channel receiver 26 of the mobile radio station 11.sub.1 from a mobile 
vehicle M, the receiver 26 sends to the combined encoder and decoder 74 of 
the mobile control unit 12 a control data which is formed by adding the 
received signal level to the received origination signal and shown in FIG. 
7B through control channel 16B. In response to the output of the combined 
encoder and decoder 74 the sequence controller 76 performs the origination 
sequence processing as shown in FIG. 8. 
When the sequence controller 76 is informed by the output of the combined 
encoder and decoder 74 of the origination of the vehicle (step 121), a 
mobile station identification information, a radio zone information, a 
signal type information and a level information are stored in a temporary 
memory device, not shown. Then, the mobile base station from which the 
strongest signal has been received is determined in accordance with 
various information described above sent from respective mobile base 
stations (step 122) so as to search whether there is an idle speech 
channel or not in the speech channels belonging to said mobile base 
station (step 123). The method of searching is fully described in a 
copending U.S. Patent application Ser. No. 760,124 filed on Jan. 17, 1977 
under a title of "A method of assigning a radio channel to a calling 
mobile body of a mobile communication system and radio channel assigning 
therefor" so that the method will not be described in this specification. 
In the absence of an idle speech channel, an idle speech channel of a radio 
zone having the second largest wave level is searched and if search is in 
vain, the system is returned to the waiting state, and the release 
processing is performed (step 214). On the other hand, where a idle speech 
channel is found in step 123, the sequence controller 76 determines 
whether there is an wave interference or not in the selected idle speech 
channel by determining whether there is a on-signal or not on the up path 
signal line 15.sub.a and the down path signal line (step 125). If there is 
an on-signal on these signal lines the sequence controller 76 advances to 
step 126 for selecting another idle speech channel and executes the 
sequence of the step 125 on the another idle speech channel. In the 
absence of any idle speech channel the release processing is performed 
(step 124). 
Where there is no wave interference on the selected idle speech channel, 
the sequence controller 76 writes the data regarding this idle speech 
channel in a SPU correspondence memory device, not shown, and then 
advances to the next step 127 thereby performing a channel designation 
processing. More particularly, the sequence controller 76 forms a control 
data, that is a channel designation signal shown in FIG. 7C by combining 
the information regarding the selected idle speech channel with the 
identification number information of the vehicle M which has been 
temporarily stored in the temporary memory device, and sends this control 
data to the combined encoder and decoder 74 which transmits the control 
data to the mobile base stations 11.sub.1 through 11.sub.n via the control 
channel 16.sub.a. 
At the same time, the sequence controller 76 designates a SPU (speech path 
unit) address corresponding to the selected speech channel and sends the 
information regarding the designated address to the SPU controller 80 via 
the address bus line 86. As a consequence, the SPU controller 80 sends an 
on-signal to the BD down path signal line 15.sub.b corresponding to the 
selected speech channel thereby turning OFF the source of the speech 
channel transmitter 23 of the mobile base station 11.sub.1. Then the 
sequence controller 76 controls the speech path unit 71 via the SPU 
controller 80 to perform a loop check test of the radio speech channel 
(step 128). When the result of this loop check test is satisfactory an 
origination signal having a pattern as shown in FIG. 7D is sent to the 
mobile exchange unit 13 via the combined encoder and decoder 88. At the 
same time, the sequence controller 76 controls the speech path unit 71 via 
the SPU controller 80 for sending an ground signal to the CU up path 
signal line 18.sub.a (step 129). The CU on-signal means that the mobile 
exchange unit 13 has completed the checking of the designated speech 
channel. Accordingly, the information sent through the common control 
channel and the information exchanged between the mobile exchange unit and 
the mobile control unit through signal lines are doubly checked. 
Accordingly, the reliability of the control operation when the mobile 
control unit advances to the next step is improved. 
As the mobile exchange unit 13 receives the origination signal from the 
combined encoder and decoder 91 through the common control line 196 (step 
131 shown in FIG. 8A), the sequence controller 94 temporarily stores this 
data in the temporary memory device 99 and then selects a bidirectional or 
both way trunk line, and an output trunk line corresponding to the speech 
channel number information of that data (step 132). 
Then the sequence controller 94 operates to check whether there is an 
on-signal on the up path signal line 18.sub.a of the both way trunk or not 
(step 133) thereby performing the loop check test of the ordinary 
telephone system. If there is no on-signal, an on-signal is sent to the 
down path signal line 18.sub.b from the both way trunk 103 (step 134). 
When the sequence controller 76 of the mobile control unit 12 receives the 
CD on-signal on the down path signal line 18.sub.b (step 136 shown in FIG. 
8B), the speech path unit 71 supplies a dial tone sending command signal 
to the down path speech channel 15.sub.b through the SPU controller 80 
(step 137). 
When a dial signal is sent to the mobile exchange unit 13 from the mobile 
vehicle M via SPU 71 of the mobile control unit 12 (step 140 shown in FIG. 
8C), the sequence controller 94 analyzes the dial signal (step 141) and if 
the dial is satisfactory it removes the CD on-signal from the down path 
signal line 18.sub.b (step 142). Further, since the mobile control unit 12 
receives the release or open signal of the down path signal line 18.sub.b 
from the mobile exchange unit 13 ((step 147 shown in FIG. 8D) it is noted 
that the dial tone is normal. After repeating the ring back tone to the 
vehicle M (step 148) the sequence controller 94 performs the outgoing 
connection processing (step 143) to send a call tone to the called party 
or subscriber and a ring back tone to the vehicle M (step 143). When the 
called party responds (step 144), the down path signal line 18.sub.b is 
again applied with a CD on-signal (step 145) thus terminating the 
origination operation. Thus, when the fact that a CD on-signal has been 
applied to the down path signal line 18.sub.b from the mobile exchange 
unit 13 is detected, the origination operation is terminated and speech is 
commenced. This transfer of the steps is effected by using the content of 
the SPU corresponding memory device. 
Paging Operation of the Mobile Control Unit 12 and the Mobile Exchange Unit 
13 
Where there is a paging, the mobile exchange unit 13 analyzes the paging 
and thereafter sends a control data as shown in FIG. 9A to the combined 
encoder and decoder 88 via the common control line 19.sub.a. 
After storing the data concerning the paging in a temporary memory device, 
not shown, the sequence controller 76 causes all mobile base stations to 
send control data shown in FIG. 9B via the combined encoder and decoder 74 
and the common control line 16.sub.a thereby simultaneously calling the 
mobile vehicles M. 
On the other hand, when a paging response is received from the vehicle M 
the sequence controller 76 executes the steps 121 through 125 among the 
sequences of the origination operation shown in FIG. 8. Similar to the 
origination operation, the sequence controller 76 sends to the vehicle M 
the speech channel disignation data shown in FIG. 9C via the common 
control channel 16.sub.a and the mobile base station so as to send a BD 
on-signal to the down path signal line 15.sub.b thus turning on the source 
of the transmitter 23 of the mobile base station. Then the sequence 
controller 76 performs the loop check test of the radio speech channel 
loop and when the channel is available, it sends a paging response signal 
of the pattern shown in FIG. 9C to the mobile exchange unit 13 via the 
common control line 19.sub.b. 
When the sequence controller 94 of the mobile exchange unit 13 receives the 
paging response signal it catches the both way trunk 103 to connect to the 
MLCT 109 thereby performing the check test of the speech channel loop of 
the ordinary telephone system. If the channel loop is available the 
sequence controller 94 sends a CD on-signal to the down path signal line 
18.sub.b through the both way trunk 103. Then, the sequence controller 94 
sends a call tone to the vehicle and a ring back tone to the originating 
side. 
When the vehicle responds by hooking off, the sequence controller 76 of the 
mobile control unit 12 applies a CU on-signal to the up path signal line 
18.sub.a. 
When the sequence controller 94 of the mobile exchange unit 13 detects this 
CU on-signal on the up path signal line, speech is commenced. 
Speech Termination Operation of the Mobile Control Unit 12 and the Mobile 
Exchange Unit 13 
The speech termination operation of the mobile control unit 12 and the 
mobile exchange unit 13 will now be described with reference to the flow 
chart shown in FIG. 12 which shows the operation of the mobile control 
unit 12. 
When a subscriber on the side of the mobile exchange unit 13, that is on 
the side of the ordinary telephone system firstly hooks on a speech 
termination is detected on the side of the mobile exchange unit 13. Then 
the exchange unit 13 performs such predetermined speech termination 
operation as charge stop and then the sequence controller 94 makes an 
access to the both way trunk 103 to remove the CD on-signal from the down 
path signal line 18.sub.b. 
As a consequence, in response to the opening of the down path signal line 
18.sub.b (step 515), the sequence controller 76 of the mobile control unit 
12 causes the SPU 71 to remove the BD on-signal from the down path signal 
line 15.sub.b via the SPU controller 152 (step 152). Consequently, after 
sending a release signal, the transmitter 23 of the mobile base station 
11.sub.1 turns off the source. 
Upon receiving an on hook tone from the vehicle M (step 153), the sequence 
controller 76 removes the CU on-signal from the up path signal line 
18.sub.a (step 154) to write an idle state in the SPU correspondence 
memory device, not shown, thereby displaying the idle state of a 
corresponding speech channel of the idle speech channel memory device 28 
(step 155). At this time, the speech termination operation is completed. 
Of course, on the side of the mobile exchange unit, a well known speech 
termination processing such as charging stop is performed. 
When the subscriber of the vehicle M firstly hooks on, a speech termination 
tone is sent from the vehicle M in response to the hook on operation, for 
example. As the sequence controller 76 receives this speech termination 
tone via SPU 71 (step 157), it removes the CU on-signal from the up path 
signal line 18.sub.a (step 158) whereby the mobile exchange unit 13 
executes such predetermined speech termination sequence as the charge 
stopping. When supplied with the speech termination signal from the 
ordinary telephone system the mobile exchange unit 13 removes the CD 
on-signal from the down path signal line 18.sub.b. 
When the release of the down path signal line 18.sub.b is detected (step 
159) the sequence controller 76 will cause SPU 71 to remove the BD 
on-signal from the down path signal line 15.sub.b via the SPU controller 
81 (step 160). As a consequence, the transmitter of the mobile base 
station transmits a release signal to turn off the source of the 
transmitter. 
Upon receiving an on hook tone from the vehicle M (step 161) the sequence 
controller 76 stores the information of the idle speech channel in a 
corresponding SPU memory device, not shown, thereby causing the 
corresponding channel of the idle channel memory device 28 to display the 
idle channel (step 162). At this time, the speech termination operation is 
completed. 
In the foregoing description, the speech termination operation was 
described mainly with reference to the sequence controller 76 and circuit 
elements associated therewith. However, there is a case that the sequence 
controller 76 can not operate due to the interruption of the source caused 
by a system fault. In such a case, the BD on-signal will not be applied to 
the down path signal line 15.sub.b. Under these conditions, when the down 
path signal line 15.sub.b is opened, the transmitter 23 of the mobile base 
station transmits a release signal thus turning off the source of the 
transmitter. 
Control Operation when the Content of the Idle Speech Channel Memory Device 
is different from the Actual State of the Speech Channel 
Since this operation renders the content of the idle speech channel memory 
device that stores the state of the speech channel to be the same as the 
actual state of the speech channel, if they do not coincide each other, 
the content of the idle channel memory device is corrected to become equal 
to the actual state or an alarm is operated, if desired. 
The sequence controller 76 of the mobile control unit 12 shown in FIG. 6 
starts a scanner in response to a timing pulse generated by the timing 
circuit 79. This timing pulse is generated by the timing circuit when a 
time out or time over occurs during the course of the origination or 
paging. Alternatively, the timing signal is generated when the origination 
or paging sequence terminates. The scanner 81 begins its scanning 
operation when it receives the timing pulse for checking the states of the 
down path signal line 15.sub.a and the up path signal line 18.sub.b 
thereby sequentially sending out these states. The sequence controller 76 
compares the output of the scanner 81 with the corresponding channel 
content of the idle channel memory device 78. If they differ, the sequence 
controller 76 rewrites the content of the idle speech channel memory 
device 78 or sends an alarm signal. 
Speech Path Unit (SPU) 71 and its Peripheral Circuits 
With reference now to FIGS. 10A and 10B the detail of the speech path unit 
71 and its peripheral circuits of the radio control unit will be described 
hereunder. The speech path unit 71 operates to check whether a speech 
channel has been established or not to the vehicle via the mobile base 
section 11, to repeat a dial signal from the vehicle M to the mobile 
exchange unit 13, and to confirm that speech channel has been established 
between the mobile exchange unit 13 and the ordinary telephone system by 
utilizing the signal lines provided by this invention. 
The relationship between the SPU 71 and the states of respective speech 
channels is as follows. 
To establish an origination connection the sequence controller 76 selects 
an idle speech channel from the content of the idle speech channel memory 
device in response to an origination signal from the mobile base station 
11. The sequence controller 76 makes an access to the address decoder 190 
of the SPU controller 80 for the purpose of checking the actual state of 
the selected idle speech channel (step 125, shown in FIG. 8) thereby 
setting flip-flop circuits 192 and 193. If this speech channel is free 
from any wave interference, BU on detector 194 will not produce any output 
and an output is produced via an inverter 195 and a NAND gate circuit 196. 
The output of the NAND gate circuit 196 is derived out through a SPU 
encoder 197. Under these conditions the sequence controller 76 advances to 
the succeeding step (step 127 shown in FIG. 8). If the speech channel is 
subjected to a wave interference, the up path signal line 15.sub.a is 
applied with a BU on-signal so that the output of the BU on detector 194 
would be derived out through the NAND gate circuit 198. At this time, the 
sequence controller 76 selects another idle speech channel, and operates 
an alarm, if desired. When the sequence controller 76 judges that the idle 
speech channel is free from any wave interference, a control data 
information shown in FIG. 7C is sent to the vehicle M via the mobile base 
station 11 (step 127 shown in FIG. 8). At the same time, the sequence 
controller 76 commonds to apply a BD on-signal to the down path signal 
line 15.sub.b corresponding to the idle speech channel. This command is 
sent to the address decoder 190 of the SPU controller 80 and the output 
thereof sets a flip-flop circuit 199 and energizes a relay 201 via an OR 
gate circuit 201 thereby turning on the down path signal line 15.sub.b. By 
applying a BU on-signal to this signal line, the source of the transmitter 
23 of the mobile base station 11 is turned on. 
The sequence controller 76 advances to the step 128 shown in FIG. 8 so as 
to set a flip-flop circuit 202 concurrently with the operation described 
above, thus opening a gate circuit 203. At this time, the sequence 
controller 76 sets a flip-flop circuit 204 to prepare to receive a signal 
showing that the radio speech channel loop is available via the gate 
circuit 203, a receiver 204 and a NAND gate circuit 205. Then the sequence 
controller 76 sends to the address decoder 190 of the SPU controller 80 to 
cause it to produce a signal for confirming the presence of a speech 
channel loop. This signal is decoded by the address decoder 190 and then 
utilized to set a flip-flop circuit 206 for opening a gate circuit 207 
thus sending a loop confirmation tone to the down path speech channel 
14.sub.b from an oscillator 208. In the mobile base station 11, this loop 
confirmation tone is modulated and then transmitted to the vehicle M. 
When the receiver 204 receives a loop confirmation response tone from the 
vehicle, this tone is sent to the encoder 197 and the process request 
detector 211 of the SPU controller 80. The output of the process request 
detector 211 is sent to the sequence controller 76 via a sense port 82. 
Accordingly, the sequence controller 76 sends an address data to the SPU 
controller 80 for confirming that there is a loop confirmation response by 
analyzing the content of the encoder 210. 
When the loop confirmation response is made the sequence controller 76 
advances to step 129 shown in FIG. 8 for transmitting the data regarding 
the origination to the mboile control unit 13 via the combined encoder and 
decoder 88. This data has a construction as shown in FIG. 7D. Concurrently 
therewith, the sequence controller 76 sets a flip-flop circuit 213 via the 
address decoder 196 to energize a relay 215 via an OR gate circuit 214 
thereby applying a CU on-signal to the up path signal line 18.sub.a 
connected to the mobile exchange unit 13. 
Concurrently with the operations described above, since the sequence 
controller 76 receives a speech channel loop check test tone between it 
and the mobile exchange unit 13, it sets a flip-flop circuit 217. Also the 
flip-flop circuits 204 and 206 utilized for the loop confirmation test to 
the vehicle M are set. 
When a well known origination processing is performed in the mobile 
exchange unit 13 an ordinary telephone loop confirmation signal is 
transmitted to the down path speech channel via the both way trunk 103 
(step 134, shown in FIG. 8A). When the receiver 218 receives this loop 
confirmation signal, it sends its output to the encoder 197 and the 
process request detector 211 of the SPU controller 80 via an NAND gate 
circuit 219. As the sequence controller 76 receives the output of the 
process request detector 211 via the sense pole 82, it sets a flip-flop 
circuit 220 to send an ordinary telephone system loop confirmation 
response tone to the up path speech channel 17.sub.a from oscillator 221 
via a gate circuit 222. At the same time, a flip-flop circuit 224 is set 
by the output of the address decoder 190 thus preparing to receive the CD 
on detection signal of the down path signal line 18.sub.b which is sent 
from the mobile exchange unit 13 in accordance with the ordinary telephone 
system loop confirmation response tone, by the CD on detector 225 via a 
NAND gate circuit 226. 
When the ground signal of the down path signal line 18.sub.b is detected by 
the CD on detector 225 of the down path signal line (step 136 of FIG. 8B), 
the output of this detector 225 is sent to the encoder 197 and the process 
request detector 211 via NAND gate circuit 226. In response to the output 
of the encoder 197 for the sense port 82 and the SPU controller 80, the 
sequence controller 76 analyzes the data and when it judges that a speech 
channel loop of an ordinary telephone system is available, it resets 
flip-flop circuits 220 and 217. 
Then, the sequence controller 76 sets a flip-flop circuit 230 via the 
address decoder 190 of the SPU controller 80 thereby sending a tone signal 
that commands the transmission of a dial tone to the down path speech 
channel 14.sub.b from the oscillator 231 via the gate circuit 232 (step 
137, shown in FIG. 8B). At the same time, flip-flop circuit 238 is also 
set to establish a speech channel to the mobile exchange unit 13. 
Also the flip-flop circuit 241 is set to enable to detect whether the down 
path signal line 18.sub.b has been released or not via the CD on detector 
225, inverter 242 and NAND gate circuit 243. 
The dial tone from the vehicle M is sent to the mobile exchange unit 13 via 
the SPU 71 (step 140, shown in FIG. 8C) for checking that whether the dial 
tone has been correctly received by the mobile exchange unit 13 or not 
(step 141 shown in FIG. 8C). If the dial tone was correctly received the 
sequence controller 94 of the mobile exchange unit 13 removes the DE 
on-signal from the down path signal line 14.sub.b through the both way 
trunk 103 (step 142 shown in FIG. 8C). If the dial tone is not correct at 
this time, this fact is transmitted to the mobile control unit 12 from the 
mobile exchange unit 13 through the combined encoder and decoder 91, thus 
executing an release processing. 
When the release of the down path signal line 18.sub.b is detected by the 
detector 225, this fact is transmitted to the encoder 197 and process 
request detector 211 of the SPU controller 80 via inverter 242 and NAND 
gate circuit 243, and the output of the detector 211 is sent to the sense 
port 82. 
When the sequence controller 76 confirms the release of the down path 
signal line 18.sub.b, flip-flop circuits 230 and 241 are reset for 
generating a tone signal that commands the sending of a dial tone. 
When the called subscriber responds (step 144 shown in FIG. 8C) the 
sequence controller 94 of the mobile exchange unit 13 again applies a CD 
on-signal to the down path signal line 18.sub.b through the body way trunk 
103 thereby putting the SPU in the speech state. 
When the sequence controller 76 controls via inverter 242, NAND gate 
circuit 243, adapted to detect the speech termination tone from the 
vehicle and NAND gate circuit 243 via inverter 242 so as to detect the 
release of the down path signal line 18.sub.b extending from the mobile 
exchange unit 13, at the time of speech termination on the paging side. 
The paging connection operation of the SPU 71 will now be described. 
When the mobile control unit 12 is informed of the paging from the mobile 
exchange unit 13 through the common control line 19.sub.a, it sends a 
paging information to the mobile base stations 11 via the common control 
line 16.sub.a thereby radiating electric waves from the antenna 20 of all 
mobile base stations 11. 
When a response signal from the mobile vehicle M is detected, a radio zone 
is selected in the same manner as the origination connection described 
above for selecting an idle speech channel from the idle speech channel 
memory device, and the presence or absence of a wave interference of the 
selected idle speech channel is confirmed through the up path signal line 
15.sub.a. In the same manner as the origination connection operation, when 
the idle speech channel is selected, the sequence controller 76 sets the 
flip-flop circuits 192 and 193 via the address decoder 190 of the SPU 
controller 80 thereby judging the presence or absence of the interference 
in accordance with the outputs produced at that time by the NAND gate 
circuits 199 and 196. 
When the absence of the wave interference of the selected idle speech 
channel is confirmed, the sequence controller 76 sends a paging response 
signal to the mobile exchange unit 13 via the common control line. At the 
same time, the flip-flop circuit 224 for detecting the CD on-signal on the 
down path signal line 18.sub.b is set. 
In response to the above described control data, the mobile exchange unit 
13 selects a speech channel and applies a CD on-signal to the down path 
signal line 18.sub.b. When the sequence controller 76 confirms the 
application of the CD on-signal to the signal line 18.sub.b, it sends an 
information shown in FIG. 9C and containing a speech channel number to the 
vehicle M from the mobile base station via the common control line. 
Thereafter, the operations between the vehicle M and the mobile control 
unit 12 are performed in the same manner as the above described operations 
for the origination connection until the BD on-signal is applied to the 
down path signal line 15.sub.b thereby performing the confirmation test of 
the radio speech channel loop. 
When the receiver 204 of SPU 71 receives a radio side loop confirmation 
response signal its output is sent to the sense port 82 via NAND gate 
circuit 205, the encoder 197 and the process request detection circuit 211 
of the SPU controller 80. When the sequence controller 76 confirms the 
establishment of the radio side loop it sets the flip-flop circuit 230 via 
the address decoder 190 thereby sending a call tone sending command signal 
for the vehicle M to the down path speech channel 14.sub.b from the 
oscillator 231 via the gate circuit 232. At the same time, the flip-flop 
circuit 251 is set via the address decoder 190 so as to receive the 
response tone from the vehicle M by the receiver 252 via NAND gate circuit 
253. 
When the handset of the vehicle M is hooked off to produce a response tone, 
this tone is received by the receiver 252 and then sent to the sense port 
82 via the encoder 197 and the process request detection circuit 211 of 
the SPU controller 80. When the sequence controller 76 confirms the 
vehicle response by the output of the receiver 252, the flip-flop circuit 
230 is set via the address decoder 190. At the same time, the flip-flop 
circuit 213 is set via the address decoder 190 to apply a CU on-signal to 
the up path signal line 18.sub.a by energizing relay 215. This informs to 
the mobile exchange unit 13 the fact that the vehicle M has responded, and 
the speech state is established. Then, the flip-flop circuit 241 is set to 
enable the speech termination tone detection NAND gate circuit 246 and the 
NAND gate circuit 243 adapted to detect the release of the down path 
signal line 18.sub.b their terminating the paging processing. 
The speech termination operation of SPU 71 is as follows. 
Assume now that the handset of the vehicle M is hooked on the speech 
termination tone is firstly sent. During the speech state, flip-flop 
circuits 202 and 238 are set and the flip-flop circuit 249 is also set. 
Under these conditions, when the receiver 245 detects the speech 
termination tone the output of the receiver is sent to the sense port 82 
via the NAND gate circuit 246, encoder 197 and process request detector 
211. 
Thus, when the sense port 82 confirms the receival of the speech 
termination tone the flip-flop circuit 260 is set to deenergize relay 215 
thus removing the CU on-signal from the up path signal line 18.sub.a. 
Concurrently therewith, the flip-flop circuit 241 is set to enable the 
NAND gate circuit 243 adapted to detect the release of the signal line 
18.sub.a. 
When the down path signal line 18.sub.b is released, the mobile exchange 
unit 13 executes a predetermined speech termination processing (for 
example, charging stop) and thereafter the sequence controller 94 removes 
the CD on-signal from the down path signal line 18.sub.b via the both way 
trunk 103. 
When the CD on detector 225 of the mobile control unit 12 detects the 
release of the signal line via inverter 242 and NAND gate circuit 243 the 
sequence controller 76 sets the flip-flop circuit 264 via the address 
decoder 190 thus removing the BU on-signal from the down path signal line 
15.sub.b. At the same time, the NAND gate circuit 253 adapted to derive 
out the output of the interruption tone receiver 252 is enabled by setting 
the flip-flop circuit 251. 
Upon detection of the interruption of the BD descending signal line 
15.sub.b, the mobile base station sends an interruption signal to the 
vehicle M. In this manner, the OFF control operation of the transmitter 23 
of the mobile base station 11 is performed. 
When the receiver 252 confirms that the vehicle has sent the on hook tone 
in response to the release signal, its output is sent to the sense port 82 
via the NAND gate circuit 253, encoder 197 and the process request 
detection circuit 221 of the SPU controller 80. Thus, when the sequence 
controller 76 confirms the on hook tone it resets the flip-flop circuit 
251 via the address decoder 190 to erase the content of the idle speech 
channel memory circuit thereby terminating the speech termination 
operation. 
Now a case wherein the ordinary telephone system side terminates speech 
prior to the vehicle will be described. When the sequence controller 94 of 
the mobile exchange unit 13 confirms the speed termination on the ordinary 
telephone system side in a manner well known in the art, the sequence 
controller 94 stops charging and the removes the CD on-signal from the 
down path signal line 18.sub.b via the both way trunk 103. 
Accordingly, the NAND gate circuit 243 is enabled through the CD on 
detector 225 and inverter 242 of the SPU 71 to detect the release of the 
down path signal line 18.sub.b. When the sequence controller 76 confirms 
this via the encoder 97 and the sense port 82, the flip-flop circuit 262 
is set via the address decoder 190 thus removing the BD on-signal from the 
down path signal line 15.sub.b. Concurrently therewith, the flip-flop 
circuit 251 is set to enable the NAND gate circuit 253 of the on hook tone 
receiver 252. 
Since the BD on-signal has been removed from the down path signal line 
15.sub.b the mobile base station 11 transmits an interruption signal to 
the vehicle M. Accordingly, the vehicle M performs the release operation 
and the on hook signal is sent to the mobile base station 11, and this 
signal is detected by the on hook tone receiver 252 of the SPU 71. When 
the sequence controller 76 confirms this it sets the flip-flop circuit 760 
whereby the relay 215 is deenergized to remove the CU on-signal from the 
up path signal line 18.sub.a. At the same time, the corresponding memory 
of the idle channel speech channel memory device is erased thus 
terminating the speech termination operation. 
To normally supervise the idle speech channel NAND gate circuits 270 and 
271 are utilized. One input of the NAND gate circuit 270 is connected to 
the output of the BU on detector 194 for supervising the state of the 
speech channel on the radio side, whereas one input of the NAND gate 
circuit 271 is connected to the output of the CD on detector 225 for 
supervising the state of the speech channel of the ordinary telephone 
system side. The other inputs of these NAND gate circuit are connected to 
receive the scanning signal from the scanner 81. The combination of these 
NAND gate circuits is provided for each speech channel, and the outputs of 
all NAND gate circuits are commonly applied to one input of a NAND gate 
circuit 280 for scanner 281. Similarly, the outputs of all NAND gate 
circuits 271 are commonly applied to one input of a NAND gate circuit 281 
for the scanner 81. 
When the scanner 81 receives a timing pulse from the sequence controller 76 
due to time over of the sequence, a scanning signal is applied to these 
NAND gate circuits 270 and 271. When an on-signal is applied to the up and 
down path signal lines 15.sub.a and 18.sub.b, these NAND gate circuits 270 
and 271 produce outputs. On the contrary, when the on-signal is not 
applied to the up and down path signal lines 15.sub.a and 18.sub.b, these 
NAND gate circuits do not produce any output. The outputs of the NAND gate 
circuits are sent out, on the time division basis, from the scanner via 
the NAND gate circuits 280 and 281 associated therewith. 
The sequence controller 76 compares the output of the scanner 81 with the 
corresponding content of the idle speech channel memory device. When 
coincidence is obtained, the sequence controller 76 does not perform any 
function. However, when a coincidence is not obtained the content of the 
idle speech channel memory device is renewed in accordance with the data 
provided by the scanner 81. When the content is rewritten, the sequence 
controller 76 sends an alarm signal to a panel board, not shown, or sends 
a signal to an output device, not shown, to show that the content has been 
rewritten. 
The operation described above is performed for all other speech channels. 
Bidirectional Trunk 103 
One example of the both way trunk 103 which is utilized when the up path 
signal line 18.sub.a and the down path signal line 18.sub.b are provided 
in accordance with this invention will be described with reference to FIG. 
13, in which only elements directly related to this invention are shown. 
The both way trunk 103 shown in FIG. 13 comprises an address decoder 300 
controlled by the sequence controller 94 via the address bus line and an 
encoder 310 which provides an output to the data bus line from the both 
way trunk 103. The origination operation will firstly be described. A CU 
on-signal applied to the up path signal line 18.sub.a after completion of 
the radio side speech channel loop check test performed on the side of the 
mobile control unit 12 is detected by a CU on detector 320 of the both way 
trunk 103. At this time, the address coder 300 resets the flip-flop 
circuit 321 under the control of the sequence controller 94 whereas a gate 
signal is sent to the NAND gate circuit 322. Consequently, when the CU 
on-signal is detected by the CU on detector 320, the flip-flop circuit 321 
is set via the NAND gate circuit 322 and its output is sent out via the 
encoder 310. In response to this output and the control data sent from the 
mobile control unit 12 through the common control line 19.sub.b the 
sequence controller 94 executes a predetermined origination processing 
sequence. 
When the above described origination or paging processing sequence 
terminates the sequence controller 94 sets the flip-flop circuit 325 via 
the address decoder 300 so as to send an output to the down path signal 
line 17.sub.b from the oscillator 325 via the gate circuit 327 thus 
performing the loop check test of the ordinary telephone system side 
speech channel. At the same time, the flip-flop circuit 330 is set and the 
flip-flop circuit 331 is reset. On the other hand, when a response signal 
is sent to the up path speech channel 17.sub.a from the SPU 71 of the 
mobile control unit 12, this response signal is received by a receiver 332 
of the both way trunk 103. Accordingly, the output of the receiver 332 is 
applied to an encoder 310 via NAND gate circuit 333 and a flip-flop 
circuit 331. From the output of this encoder the sequence controller 94 
judges that the result of the speech channel loop check test is 
satisfactory and sets a flip-flop circuit 335 through an address decoder 
350. Thus, relay 336 is energized for applying a CD on-signal to the down 
path signal line 18.sub.b. At this time, flip-flop circuits 325 and 330 
are set. 
Thereafter, when a dial tone sent to the both way trunk 103 through the up 
path speech channel 17.sub.a is normal, the sequence controller 94 
operates to set a flip-flop circuit 340 via the address decoder 300 to 
deenergize relay 336 which has been energized up to this time for removing 
the CD on-signal from the down path signal line 18.sub.b. Then the 
flip-flop circuit 335 is reset. 
When the sequence controller 94 knows that the called party has responded 
it sets again the flip-flop circuit 335 and resets the flip-flop circuit 
340 via the address decoder 300 to deenergize relay 336 thereby applying 
the CD on-signal to the down path signal line 18.sub.b. Furthermore, the 
flip-flop circuit 342 is set thereby terminating the origination 
operation. At this time, the flip-flop circuit 340 is reset. 
At the time of paging the paging data are sent to the mobile control unit 
12 over the common control line so that the both way trunk line 103 
operates in the same manner as above described. 
The speech termination operation is effected in the following manner. When 
the subscriber of the ordinary telephone system firstly hooks on, the 
sequence controller 94 sets the flip-flop circuit 340 via the address 
decoder 300 to deenergize relay 336 whereby the CD on-signal is removed 
from the down path signal line 18.sub.b. 
Thereafter, the CU on-signal which has been applied to the up path signal 
line 18.sub.a from the SPU 12 of the mobile control unit 71 is removed to 
render the signal line to be available. At this time, the flip-flop 
circuit 342 is set and the NAND gate circuit 343 is enabled by the output 
of the address decoder 300 so that its output is applied to the encoder 
310 via inverter 344. The sequence controller 94 knows that the speech 
termination operation has been completed from the output of the encoder 
310. 
On the other hand, when the subscriber of the vehicle M firstly hooks on 
the CU on-signal is removed from the up path signal line 18.sub.a and then 
the relay 336 is deenergized to remove the CD on-signal from the down path 
signal line 18.sub.b. For this reason, similar operations are made except 
that the sequence of operations is reversed from that when the hook on is 
firstly made on the side of the ordinary telephone system. 
While the invention has been shown and described in terms of a preferred 
embodiment thereof it should be understood that many changes and 
modifications will be obvious to one skilled in the art without departing 
from the spirit and scope of the invention as defined in the appended 
claims.