Note: Descriptions are shown in the official language in which they were submitted.
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1 This invention relates to a selective calling system and,
more particularly, to a receiving sub-system for the selective calling
system which feeds a display system - particularly of the digital type.
Conventionally, there exist systems for detectine an analogue
signal as the calling message by use of mechanical filters and systems
employing a digital code signal as the calling message.
It is noted that in systems employing the digital code signal,
it is generally possible to have many more messages than in systems
employing analogue sig~als.
However, such digital code systems generally have no storage
circuits and cannot confirm the messages to be displayed if t'he message
transmitted from the transmitter of the main system is erased with 'the
operation of the reset means from the display.
Accordingly, such digital code systems do not utilize all
messages transmitted from the transmitter of the main-system. -
It is therefore an ob~ect of this invention to provide a ~ '
- selective calling'system eliminating the above drawback.
Thus, according to the present invention, we provide:
' a receiving sub-system for use in a selective calling system
employing a digital display means, said sub-system comprising:
a) a sign discriminator;
b) a plurality of storage circuits connected to an output from '-
said sign discriminator;
c) a first switch connected with an output from said sign
di'scriminator;
d) a plurality of second switches respectively connected with '~-
the outputs from said storage circults; ~'
e) a switch control section controlling the conductance state -' -
of each o~ said first and secon~ switches;
~ f) a storage calling section selectively controllin~ said
switch control section;
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1 g) said swit.ches connected between said sign discriminator
or said s~orage ci~cuits and a display means adapted to selectively
display either the accumulated content of said sign discriminator or one
of said storage circuits, respectively, by the operation of said storage
calling section.
The invention will now be described further by way of example
only and with reférence to the accompanying drawings, wherein:
Figure 1 is a block diagram of the invention according to a
preferred embodiment thereof; and
Figure 2 is a circuit diagram showing details of Figure 1. :~
Referring now to Figure 1, the circuit comprises a receiving
section 1, a filter 2, a wave shaper 3, a sign discriminator 4, a sounding
section 5, an oscillator 10 and a display 6. These elements are themselves
conventional and therefore require no detailed description.
A message storage and switching-circuit ~ i9 connected between
the sign discriminator 4 and the dlsplay 6, and this circuit eunctions
to sequentially s~ore messages from the sign discrimination and, upon
command, apply such messages to the display 6. Basically, the circuit.7 .
comprises storage circuits Ml - Mn, respectively, having n flip-flops,
20. n+l switching circults Sl - Sn+l, a storage calling section 8 and a switch ~.
control section 9, the operations of which ~ill hereinafter be described . .
. in more detail.
Referring now to the overall system, the sign discriminator 4
detects the incoming signal, whereby the sounding sectlon 5 operates.
The operator holding the receiver (not shown) for the selective calling :: .
system confirms that he is called with the sound. The output (transmitted
message) from the sign discriminator 4 is applied to the storage circuit ~.
and at the same time is applied to the i~put terminal of the switch Sl. ~ ~
In lts normal state, the switch Sl is closed so as to connect términal a . :
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thereof with output termillal b so that the t~ansmitted message is passedto the display 6.
When the next incomlng calling message is recelved ~rom
the transmitter o~ the maln system at the receiving sectlon 1 o~ the
sub-system, the message is d~splayed at the dlsplay 6 and at the same
time is accumulated ln the storage clrcuit M~
At this time, the electric signal applied to the sounding
section 5 is applied to the storage circuit Ml whereby the content
previously stored in the storage circult Ml is shi~ted to the storage
circuit M2 to make way for the new message in the circuit Ml. Thus, the
storage circuit Ml always holds the last incoming message at any given
time, since the previous messages are shlfted in order from the circuit
Ml towards the circuit Mn, as new messages are received.
The respective contents of the storage circuits ~1 ~ Mn
are not applied to the display 6 since the tenmlnals X2 - Xn~l of the
switches S2 - Sn~l are not connected wlth the terminals Y2 ~ Yn~l in the
normal condition of the circuit. However, the operator has only to rPad-
the contents of the storage circuits ln order to conf~rm the transmitted
message thereafter. A number o~ push buttons equal to the number of
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- 20 storage circuits ~1 ~ Mn may be arranged in the storage calling section 8,
or only one push~button may be provided. ln the Pormer case~ the operator
determines the order o~ the ~essage and is able to select the storage
circuit corresponding to that order. However~ thls arrangement suffers
from the disadvantage of size and expense consequent upon the multiplicity
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o~ push-buttons required. In the latter case, the push-button and the ~- ~
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switch control section 9 (electronlc rotary switch preferably) are com~ ~
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bined and the dlsplay 6 displays the stored messages in order. There~ore,
the operator dèpresses the calllng switch in the storage calling section 8, i
whereby the terminals of the correspondlng switch ~ ~or e~ample, the
terminal Z2 ~ the swi~ch 52 and the terminal c of the switch Sl recelve
the appropriate signal f~om the sw~tch control sectlon 9.
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Accordingl~, the terminal X2 of the swltch S2 is connected
with the terminal Y2, whereby the display 6 displays the content of the
storage circuit Ml, whllst the switch Sl is disabled to be in the non-
conductive state between the te~mlnals a and b.
Simllarly, the content of the corresponding storage circuit
is applied to the display 6 by depressing the calling button of the
storage calling section 8.
Now, the circuit structure and the operation will be
described in more detail with reference to ~igure 2.
There are n stage cascade~connected shift registers SRl
connected to the output terminal of the wave shaper 3. Shift registers
SRl - SRn ~ comprises a circuit to detect the coincidence between the
local iode number of the syste~ and the call signal. Shift registers
SRn-e~l - SRn comprise a circùit to detect the displayed content.
~ The storage circuits Ml - ~n are connected with the shift
registers SRn-~ SRn.
A clock pulse CPl of predetermined interval is applied
to thé shift registers as a gating pulse ùpon detection of the signal.
The storage clrcuits Ml - Mn, respectively, have a plurality
of the ~lip-flops - for example, the storage circuit Ml includes flip-
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flops Mll - M~ and the storage circuit Mn includes flip flops Mnl - MnJZ.
The signal applied to the sounding section 5 from the sign discriminator
4 is applied to the clock terminals of the flip-flops, whereby the signals
of the storage circuits Ml - Mn are shifted.
Switches Sl - Sn~l, respectively, include a plurality o~ -
transmission gates (for example, the switch Sl includes transmission gates
Sll - Sle and the switch Sn~l includes transmission gates S(n~
S(n~l)~.).
Push-buttons MCl ~ MCn are provided corresponding to the
number of storage circuits Ml - ~In. One terminal of each push-button
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is connected with the power source ~ss and anothe~ terminal of the push-
button is connected with the switch control clrcult 9.
The switch control circuit 9 comprises n inverters Al - An
and a NAND circuit N. Each o~ the respective in~erters is connected with
one terminal o~ an associated push-button MCl - MCn and is also connected
with the power source Vdd through an associated resistor Rl - Rn. The
output terminals of the respectlve inverters Al - An are connected with
respective switches S2 - Sn~
The output terminals of the respective push-buttons are
connected with the input terminals o~ the NAND circuit N. The output of ~ ;
the N~ND circuit N is applied to respective transmission gates of the
switch Sl.
Re~erring nbw to the operation of storing the received
message, the shift registers SRn-f~ SRn detect the messages whereby -
the respective shi~t registers are connected with the respective flip- ~
flops Mll - Mle of the storage circuit Ml so that the storage circuit Ml ;
accumulates the calling message, as the shlft registers are gated by ; -~
signal of the clock input terminal CP2.
The messages which have accumulated in the flip-~lops
Mll - Mle are shifted into the flip-flops M21 - M2e of the next storage
circuit M~ and upon rècei~ing the calling slgnal, ~he accumulated messages
o~ the pre-stage storage circuit Ml are shifted into the next storage .
circui~.
The contents which have accumulated in the flip-flops M~l -
Mm~ of the final stage storage circuit are reset when the accumulated
contents of all storage circuits fill such circuits. ~-
Referring next $o the calling operation for the accumulated ~ ;
content, in the normal condition of the clrcuit, the swi~ches MCl - MCn
o~ the storage calling section 8 are in the non-conductive state and the
respective inverters Al - An o the switch cont~ol section 9 are connected ~ -
with the power source Vdd through the respective resistors Rl - Rn.
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There~ore, the input signal of these inverters is at the
high-level state and the output level ls in the low state, whereby all of
the transmission gates S21 - S(n~l)Qare in the non-conductive state.
Also, the output oP the N~ND gate N is ln the low-level
state and the transmisslon gates S~l ~ 51~ whlch are connected with the
~AND gate N through the inverter B, are in the conductive state, since
all of the inputs of the NAND gate N are high level. ~ -
Accordingly~ the display 6, which ls connected with the
shift registers SRn-~l - SRn, dlsplays the ralling message.
~eferring now to the operatlon of displaying the accumu-
lated message in *he first stage storage circuit ~13 the switch MCl of
the storage calling section is depressed, whereby the output of the NAND
gate N is rendered high level since one of thè inputs of the NA~D gate
N is rendered low-level. Therefore, all of the transmission gate Sll -
Sle are in the non-conductive 8~ate.
The transmission gates S21 - S2e of the switch S2 are in
the conductive state since only the input of the inverter Al goes to low
level and the output of the inverter Al goes to h~gh level. Further, all
of the switches S3 - Sn~l are in the non-conducti~e state since all of
the inputs~oP the inverters A2 ~ ~n are high leve:L. Accordingly, thP
display 6, which is connected only with the storage circuit Ml, displays
only the content of the storage circuit Ml.
The contents of the other storage circuits are selectively
displayed by the display 6 in precisely analogous manner.
As mentioned above, in accordance with this invention, it
is useful that the operator can retrieve messages from the calling party
a~ter the transmission has taken place.
Also, the receiver for the selective calling system in
accordance with this inventlon can store a plurallty of calling messages.
r~he receiver for the selective calling s~stem can display
again the calling message, even if the operator resets the receiver by
mi8take or by not confirming the calling message.
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