JPS6318735A - Transmitter-receiver - Google Patents

Abstract

PURPOSE:To attain connection even if all channels are busy by searching an idle channel in 2 stages of search levels to connect a handset and a base unit. CONSTITUTION:A detection signal NSQL is used to search an idle channel and when no idle channel exists, a detection signal NSQH checks whether or not an existing channel is used by other stations. In this case, since the detection signal NSQH has a higher threshold level with respect to a reception level of a FM signal Sd than that of the detection signal NSQL level, even if the channel is busy (the signal Sd exists) by the signal NSQL possibly, when the reception level of the signal Sd exits between the threshold level (0dBu) of the signal NSQL and the threshold level (12dBu) of the signal NSQH, the channel is not used for the signal NSQH (no signal Sd exists). Thus, the channel is opened and a handset 1 is connected to a telephone line 3 via a base unit 2.

Description

[Detailed description of the invention] The invention will be explained in the following order.

A. Field of industrial application B. Summary of the invention C. Prior art D. Problem to be solved by the invention E. Means for solving the problem F. Effect G. (Figure 6) G2 Other Embodiments H Effects of the Invention A Industrial Application Field This invention relates to a transmitting/receiving device such as a cordless telephone.

B. Summary of the Invention This invention provides, for example, in a multi-channel access type cordless telephone that does not have a control channel, by connecting the handset and the base unit according to a predetermined procedure, when searching for an empty channel, all This allows the connection to be made even if the channel is busy.

C. Prior Art In general telephones, the telephone cord is connected to a rosette attached to a pillar, wall, or the like. Therefore, the range within which the telephone can be moved is determined by the length of its telephone cord, and is approximately several meters. However, in order to increase the range of movement, the phone cord is lengthened (which results in the cord getting tangled and getting in the way).

Therefore, in the United States and other countries, a telephone system called a cordless telephone is being considered.

As shown in FIG. 7, it is composed of a transmitter/receiver ta (1) called a handset and a transmitter/receiver (2) called a base unit, and a telephone line (3) is connected to the base unit (2). Along with the base unit (
2) and the handset +11 are connected by radio waves, and calls from subscribers are answered in the same way as with a general telephone set for the handset (1).

Therefore, the subscriber can freely move the hand cent (1) when making a call, for example to use the telephone outdoors. What's more, the phone cord won't get tangled or get in the way.

The distance (service area) that the handset (1) can be separated from the base unit (2) is 300 m.
That's about it. Furthermore, the frequency of radio waves used between the handset (1) and the base unit (2) is 49 MH2 band for the up channel and 46 MIIz band for the down channel, and the IO deplex channel is approved by the FCC.

Thus, this cordless telephone allows the telephone to be used conveniently.

However, in cordless telephones, 10
Even if dublevkustyannel is recognized, this one
There is no control channel provided to control which channel of the 0 channel is used for communication.

Therefore, when using a cordless telephone as an MCA system (multi-channel access system), this is realized in the following manner.

That is, in Fig. 6, the left side is the handset (1).
channels managed by the base unit (2) on the right.
) indicates the channels managed by [1] to [
10] numbers indicate channel numbers, ○ marks are empty channels, * marks are the channels you are using, and x marks are channels used by other stations.

In standby mode, the handset +1) repeatedly scans all channels (receiving channels) in order and waits for a call from the base unit (2), as shown in A of the same figure. Further, the base unit (2) similarly scans all channels repeatedly in order and waits for a call from the hand center (1).

When the handset (1) makes a call, when the handset (1) is set to talk mode, the handset +11 searches for an empty channel, as shown in Figure B, and when an empty channel is found (Fig. Now for the third
channel), the search is stopped at this empty channel, and the identification code is repeatedly sent out while waiting for the identification code to be returned.

Then, in the base unit (2), when the empty channel (third channel) is reached during scanning, an identification code is obtained, but when this identification code is obtained, scanning is stopped at this empty channel. An identification code is sent back, and from then on, the call mode is entered on that vacant channel.

In addition, when the identification code is returned to the handset (1), the handset (1) enters the call mode from □ onward using the vacant channel.

Therefore, from now on, the dialed number is sent through the vacant channel (third channel), and if the other party answers the call, the call is made.

On the other hand, when receiving a call from the telephone line (3), the handset (
1) and the base unit (2) are simply swapped, and as shown in FIG. 2C, incoming calls and subsequent calls are made in the same way using an empty channel (the 9th channel in the diagram).

D. Problem to be solved by the invention However, as mentioned above, the service area of cordless telephones is as wide as about 300 meters, so if 10 sets of cordless telephones are used at the same time, 11 sets of cordless telephones will be able to make a call. However, you may not be able to find a free channel and cannot make a call.

This invention attempts to solve these problems.

E Means to solve the problem Now, if we consider the case where a cordless telephone searches for an empty channel for making or receiving a call, this is as follows.
Each channel is selected in turn, and it is determined whether the channel is vacant or in use based on the reception level (antenna input level) of signals from other stations at that time.

That is, when a certain channel is selected, if the reception level of a signal from another station is, for example, less than OdBμ, it is regarded as an empty channel, and if it is OdBμ or more, it is regarded as a channel in use.

Therefore, even if the channels are in use, their reception levels vary.

On the other hand, audio signals are transmitted and received between the handset (1) and the base unit (2) using FM waves, but FM waves generally have a capture effect, and while FM waves are being transmitted and received, another FM wave Even if noise or noise is mixed in, as long as it is at a minute level, there is no practical problem due to the capture effect.

The present invention focuses on the above points, and when connecting the handset (1) and the base unit (2), the handset (1) is connected by performing the processing shown in FIGS. ) and the base unit (2).

Free channels are searched at two search levels.
The hand cent (1) and the base unit (2) are connected.

G Embodiment G1 First Embodiment FIG. 1 shows an example of a handset (1), (110)
is a transmitting circuit, and (120) is a receiving circuit. Also, the second
The figure shows an example of the base unit (2), where (210) is a transmitting circuit and (220) is a receiving circuit.

When transmitting a call, in the handset +11, the audio signal St from the transmitter (111'') is passed through the low frequency amplifier (112) to the PLL (113) (7) VCO.
(not shown) and is supplied to the upstream channel FM signal S
This FM signal Su is sent to the antenna (
100) and transmitted to the base unit (2).

Then, in the base unit (2), the signal (radio wave) from the handset (11) Su is connected to the antenna (200
), and the received signal Su is passed through a bandpass filter (22
1) and the mixer circuit (
At the same time, a local oscillator signal of a predetermined frequency from the PLL (224) is supplied to the mixer circuit (223).
), the signal Su is converted into an intermediate frequency signal, and this intermediate frequency signal is supplied to F through an intermediate frequency amplifier (225).
The audio signal St is demodulated by being supplied to the M demodulation circuit (226''), and this signal St is sent to the low frequency amplifier (227) -
2-wire to 4-wire conversion circuit (231) → Relay circuit (232)
is sent out to the telephone line (3) through the signal line.

In this case, the relay circuit (232) is connected to the base unit (
A line relay that turns on and off the connection between the base unit (2) and the telephone line (3), and a line relay that puts the line (3) on hold when temporarily suspending a call after the base unit (2) and the line (3) are connected. It has a hold relay etc. to keep it in place.

Also, when receiving a call, the voice signal Sr from the telephone line (3)
is supplied to the receiver (128) of the handset (1) through the same process as when transmitting a call. That is, the audio signal Sr from the line (3) is supplied to the PL; FM of the downlink channel paired with the FM signal Su
The signal Sd is converted into a signal Sd, and this signal Sd is supplied to the antenna (200) through a high frequency power amplifier (214) and a bandpass filter (215) whose pass band is all the downlink channels, and is transmitted to the handset (1). Ru.

In the handset (1), the signal Sd from the base unit (2) is received by the antenna (100), and the received signal Sd is filtered by a bandpass filter (121) whose pass band is all the downlink channels and a high frequency filter. A local oscillation signal of a predetermined frequency is supplied to the mixer circuit (123) through the amplifier (122), and a local oscillation signal of a predetermined frequency is supplied from the PLL (124) to the mixer circuit (123), so that the signal Sd becomes an intermediate frequency signal. The signal passes through an intermediate frequency amplifier (125) to an FM demodulation circuit (126).
) to demodulate the audio signal Sr, and this signal Sr
is supplied to the handset (128) through a low frequency amplifier (127).

Further, in the handset (1), (140) indicates a control circuit that controls communication channels and the like.

This control circuit (140) is composed of an l-chip type microcomputer, and (141)
(142) is a ROM in which a program is written, for example, a 4-bit parallel processing CPU.

(143) is a RAM for a work area, and (144) is an input/output port. Note that the ROM (142) is also provided with a routine (300) shown in FIG. 3, for example.

Furthermore, the microcomputer (140) has a dial key (15).
1),)-X switch (152) and ROM (153)
is connected. In this case, the dial key (151) is
The talk switch (152), a non-locking type pushbutton switch for inputting the other party's phone number, is a 3-position changeover switch for selecting the operation mode of this handset (11), and the switch (152)
When is contact 0, the power to other circuits except the microcomputer (140) is turned off (off mode), and when contact is S, the state is in standby mode to receive the signal Sd from the base unit (2), and the contact When T, handset (
1) Call letter with Tohesu Unit (2)! 3 (talk mode), and is normally connected to standby contact S.

Further, the ROM (153) is for giving an identification code It), and these keys and the ROM (151)
The outputs of (153) are supplied to the microcomputer (140).

Furthermore, (161) shows an MSK modulation circuit, which is
When a code signal such as an identification code ID and a dial signal DS is supplied from the microcomputer (140), this code signal is converted from a binary signal to an MSK signal S+++ in the audio band as shown in FIG. 5A, or as shown in FIG. 5B. MSK signal S outside the audio band on the low frequency side of signal St
11, and the signal Sm is sent to the amplifier (1
12).

In this case, the signal 5I11 in A of the same figure is the handset (1
) and the base unit (2), and for this reason, the transmission speed of the code signal modulating the signal Sm is, for example, 1.2 kb.
It is said to be a high speed of ps. In addition, the signal 5L11 in FIG.
It is used when the communication channel between the handset (1) and the base unit (2) is open and a call is being made, and therefore the transmission rate of the code signal modulating the signal sII+. The speed is, for example, 110 bps.

Further, (162) indicates a reception detection circuit, which is connected to the demodulation circuit (126), and the frequency component of the output of the demodulation circuit (126,) varies depending on the presence or absence of the signal Sd from the base unit (2). This fact is used to detect the presence or absence of the signal Sd. However, in this case, the detection circuit (16
2), the threshold level (discrimination level) for the signal Sd when detecting the presence or absence of the signal Sd is set relatively low, and when the reception level of the signal Sd at the antenna (100) is, for example, less than OdBμ, the signal Sd is received. It is assumed that the signal Sd is not
will be deemed to have been received. The detection signal N5QL of this detection circuit (162) is the Macoin (140).
supplied to

Further, (166') indicates a second reception detection circuit, which is connected to the intermediate frequency amplifier (125) and detects the level of the signal Sd from the level of the intermediate frequency signal. In this case, when the detection circuit (166) detects the level of the signal Sd, the threshold level for the signal Sd is set relatively high, and the antenna (100
), the reception level of the signal Sd is, for example, 12 dBμ.
If it is less than O, it is assumed that the signal Sd is not received.
When it is equal to or greater than dBμ, it is assumed that the signal Sd has been received. The detection signal N S Q 11 of this detection circuit (166) is then supplied to the macoin (140).

Further, (163) is an MSK demodulation return circuit, which is connected to the demodulation circuit (126) and demodulates the code signal from the MSK signal Sm sent from the base unit (2), and the demodulated signal is is supplied to the microcomputer (140).

Further, (164'I indicates a ring tone signal forming circuit, which is controlled by the microcomputer (140) and forms a ring tone signal (ring tone signal) when a call is received. is supplied to the ringer (165).

Furthermore, the signal CH specifying the channel is sent from the microcomputer (140) to PLL (113), (124).
At the same time, a signal TXEU for controlling whether or not to send out the FM signal Su is supplied to the PLL (113). Further, a muting signal MUTE is supplied from the microcomputer (140) to the amplifier (127).

Further, in the base unit 7 (2), (240) indicates a control circuit. This control circuit (240) is configured similarly to the control circuit (140) of the handset (1) and has the same functions, and corresponds to the circuits (141) to (144) of the control circuit (140''). The circuit to do this requires 10
A code in the 200s will be used instead of a code in the 0s, and the explanation will be omitted. However, the ROM (242) is provided with a routine (400') shown in FIG. 4, for example.

In addition, ROM (253) and circuits (261) to (26
6) is also similar to the ROM (153) and circuits (161) to (166) of the handset (II), and each signal is also the same, so explanations of these will also be omitted.However, the forming circuit (264) is A tone encoded signal (DTMF signal) TE corresponding to the telephone number used when calling the other party is formed.

Furthermore, (265) shows a ring tone signal detection circuit, which is connected to the telephone line (3) and detects a ring tone signal (ring tone signal) when a call is received, and the detection signal BL is supplied to the microcomputer (240).

In the handset (1) and base unit 2), the following processing is performed by the CPUs (141) and (241) according to routines (300) and (400).

That is, in the handset (1), in standby mode, the PLLs (113) and (124) are controlled by the signal CH in step (301) and set to the uplink and downlink channels corresponding to the signal CHO value. , Next, in step (302), the switching position of the talk switch (152) is checked,
In this case, it is connected to contact S in standby mode, so the process starts from step (302) to step (30).
Proceed to 3). In this step (303'), whether or not the FM signal Sd is received on the downlink channel set in step (301) is determined by the signal MS.
It is checked by the OL, and if the signal Sd is not received, the process moves from step (303) to step (304).
), and in this step (304'') the signal CI
is set as the value of the next channel (adjacent channel), and then the process returns to step (301).

Further, when the signal Sd is received in step (303), the process is performed from step (303) to step (
305), and in this step (305'), the identification code ID from the demodulation circuit (163) and the ROM (1
53) and the identification code ID of the base unit (
2), the process proceeds from step (305) to step (304').

Therefore, in (1), steps (301) to (305'') are repeated during standby, and all downlink channels are sequentially and repeatedly scanned as shown in FIG. 6A.

Furthermore, in the base unit 7) (21), steps (401) to (405) of the routine (400) are executed during standby. In this case, steps (401) to (405)
performs the same processing as steps (301) to (305), and although the explanation is omitted, step (402)
, the presence or absence of an incoming call from the outside line (3) is detected using the detection signal BL, and if there is no incoming call, the process proceeds from step (402) to step (403'). Furthermore, in step (403), instead of checking the presence or absence of the FM signal Sd in step (303), a check is made to see if the FM signal Su exists.

Therefore, in the base unit (2), steps (401') to (405) are repeated during standby, and all uplink channels are sequentially and repeatedly scanned as shown in FIG.

Furthermore, when making a call using the handset (1), the talk switch (152) is switched to the talk mode contact T. Then, this is determined in step (302), the process proceeds from step (302) to step (311), and in this step (311') step (301
) is used by another station or not is checked by signal N5QL, and if not used, the process proceeds from step (311) to step (312). and,
In this step (312), F
Sending of the M signal Su is permitted, and then the Ste knob (3
13), the identification code ID of the ROM (153) is converted into an MSK signal Sm by the modulation circuit (161) and supplied to the amplifier (112), and therefore, as shown in FIG. 301) is transmitted to the base unit (2) using the upstream channel FM signal Su set.

In this case, the identification code ID in step (313)
The transmission of the identification code IO from the base unit (2)
Assuming that there is no return, the channel scanning in the base unit (2) is repeated over at least one round period.

Then, while the base unit (2) is on standby, it sequentially scans all upstream channels by repeating steps (401) to (405). When the transmitting uplink channel is reached, the process proceeds from step (403'') to step (405), the scan is stopped, and it is determined that the identification code ID has been sent.

Then, the process moves from step (405) to step (42).
1), and in this step (421) the signal Tχ
The transmission of the FM signal Sd is permitted by the EN, and then in step (422) the identification code I of the ROM (253) is
D is converted into MSK signal 5l11 by the modulation circuit (261) and supplied to the amplifier (212), so that
As shown in step (301), the identification code ID is
The FM signal Sd of the downlink channel paired with the uplink channel set in is sent back to the hand center (1).

The process then proceeds from step (422) to step (49).
0), and in this step (490), the base unit (2) and the telephone line (3) are connected, that is, the muting of the amplifier (227) is canceled by the signal MUTE, and the relay circuit (232 ), the conversion circuit (231) and the line (3) are connected.

In addition, in the handset (11), step (31
At the same time as the identification code ID is transmitted in step (3'), the output signal of the ti adjustment circuit (163) is checked to see if the identification code ID has been returned in step (314) (actually, in step (313) ) and (314) alternately in a time-sharing manner, and the shorter of the period during which the channel scan in the base unit (2) completes one cycle and the period until the return of the identification code ID is confirmed. ).

In this case, since the base unit (2) has returned the identification code ID, the process proceeds from step (314) to step (390), and in this step (390), the handset (1) and the base unit (2) ) is connected, i.e. the channel between the handset (
In 1), the amplifier (127) is activated by the signal MUTE.
muting is canceled.

Therefore, the handset (11 is the base unit (
This means that it is connected to the telephone line (3) through 2).

Therefore, in the handset (1), the dial key (1)
51) corresponding to the other party's telephone number, the microcomputer (140) forms the corresponding dial signal DS, and the modulation circuit (161) generates the MSK signal S.
m and similarly transmitted to the base unit (2).

In the base unit (2), the demodulation circuit (
The dial signal DS is taken out from the dial signal DS (263), and based on this signal DS, the microcomputer (240'') sends the dial signal DS to the forming circuit (263).
264') is controlled to form a tone encoded signal TE corresponding to the telephone number of the other party, and this signal TE is transmitted to the telephone line (3) through an amplifier (227), a conversion circuit (231) and a relay circuit (232). sent to. Therefore, if the other party is called by this signal TH and the other party answers the call, the conversation becomes possible from then on as described above.

Note that in step (311), step (301)
) is already in use by another station, the process proceeds from step (311) to step (317);
In step (311), it is checked whether or not the free channel check has been performed for all channels, and if the check has not been performed for all channels, the process proceeds from step (317) to step (304). (304), the signal CH is set to the value of the next channel, and step (30
Return to 1).

Therefore, when the talk switch (152) is switched to the talk mode contact T, a search for an empty channel is performed using the detection signal N5QL, and if there is an empty channel, the hand sent (1) is performed using that channel. It is connected to the telephone line (3) through the base unit (2).

Further, in step (314), the base unit (
If the correct identification code ID is not returned from step 2), the process proceeds from step 314 to step 3.
15), and in this step (315) the signal T
The transmission of the signal Su is stopped by XEN, and the process then proceeds to step (304). Therefore, when the identification code ID is not returned from the base unit (2), the base unit (2) similarly transmits the signal Su on the next free channel. 2
) is called.

On the other hand, if a search is made for an empty channel using the detection signal N5QL for all channels, but there is no empty channel, the process proceeds to step (317).
Proceed to step (318) from this step (31B
), it is checked by the detection signal N5QH whether the current channel is being used by another station.

In this case, the detection signal N S Q 11 is FM
Since the threshold level for the reception level of the signal Sd is higher than the detection signal N5QL, it is assumed that the signal N5Q
Even if it is determined that the channel is in use (signal Sd is present) in L, the reception level of signal Sd is equal to the threshold level (OdBμ) in signal N5QL and t=signal N5
If between the threshold level (12 dBμ) at QB, the signal N5Q)I indicates that the channel is not used (no signal Sd).

Therefore, in this case, the process proceeds to step (318).
Proceeding to step (312), the channel is then opened as described above and the handset (1) is connected to the telephone line (3) through the base unit (2).

In this case, since the detection signal N S Q II is used to search for an empty channel, compared to the case where the detection signal 5NAL is used to search for an empty channel, the FM signals Sd, S due to other cordless telephones, noise, etc.
Although the S/N of u becomes worse, there is no problem with the audio signals St and Sr due to the capture effect.

Further, in step (318), the detection signal N5QI+
The state of the channel! 3 (presence or absence of signal Sd), if the channel is still being used (this means that the level of signal Sd is 12 dBμ or more), the process proceeds from step (318) to step (304).

Therefore, from now on, a search for an empty channel is performed using the detection signal N5Qlr with a high threshold level with respect to the signal Sd, and if there is an empty channel, the hand center (1) and the base unit (2
) are connected. Note that even during the search using this detection signal N5QH, the detection signal N
Since an empty channel is also checked using 5QL, if an empty channel is found in this detection signal N5QL, this channel is used preferentially.

Also, when there is an incoming call from the telephone line (3), steps (411) to (418) of the erasure line (400) are executed.
and step (321) of routine (300),
(322) is executed. In this case, these steps (
411') to (418) and (321), (32
2) includes steps (311) to (318) and (421)
), which performs the same processing as (422),
When there is an incoming call, the signal BL is determined in step (402), so the process proceeds from step (402) to step (411), and thereafter, as shown in FIG. Telephone line (3) is the base unit (2)
is connected to the handset (11) through the

Thus, according to the present invention, when searching for an empty channel when making a call from the handset (1) or receiving a call from the telephone line (3) in an MCA cordless telephone without a control channel, the empty channel is determined. Since the threshold level when searching is switched to two levels, low level and high level, even if all channels are busy in the first search, an empty channel can be found in the next search. , you can make calls.

Also, the further apart the handset (1) and base unit (2) are, the higher the reception level of signals Sd and Su from other stations becomes. Therefore, if the threshold level at the time of search is constant, The handset (1)
As the distance between the base unit (2) and the base unit (2) increases, it becomes difficult to find an empty channel, but in this invention,
Since the threshold level at the time of search is changed to a low level and a high level, a conversation can be made even if the distance between the handset (1) and the base unit (2) becomes long.

G2 Other embodiments In the above, the detection circuit (162) or (16
6) It is also possible to obtain the signals N5QL and N5QH from either (and (262) or (266'). Also, the circuits (161) to (164), (166) (2
61)-(264).

The operation (266>) can also be realized by software.Furthermore, the telephone number of the other party can also be sent by dial pulse.

In addition, in steps (313) and (413), the identification code ID is sent, and the FM message from the other party is sent.
Check the presence or absence of the signals Sd, Su, and check the presence or absence of the signals Sd, Su.
Once Su is obtained, step (314), (41
The identification code ID may be checked in step 4). moreover,
This invention is applicable not only to cordless telephones but also to transceivers, carrier-wave intercoms using commercial AC power lines, and the like.

Effects of the Invention According to this invention, an MC without a control channel
For A-type cordless telephones, the handset (
When searching for an empty channel when making a call (1) or receiving a call from the telephone line (3), the threshold level for determining an empty channel is switched to two levels: low level and high level. , even if all channels are busy in the first search, a free channel can be found in the next search, and therefore a call can be made.

Also, the farther apart the hand center (1) and the base unit node (2) are, the higher the reception bell of signals Sd and Su from other stations becomes. Therefore, if the threshold level at the time of search is constant, There is a hand cent (1)
As the distance between the base unit (2) and the base unit (2) increases, it becomes difficult to find an empty channel, but in this invention,
Since the threshold level at the time of search is changed to a low level and a high level, it is possible to make a call even if the distance between the handset (11) and the base unit (2) becomes long.

[Brief explanation of drawings]

FIGS. 1 and 2 are system diagrams of an example of the present invention, and FIGS. 3 to 7 are diagrams for explaining the same. (1) is the handset, (2) is the base unit, (1)
10). (210') is a transmitting circuit, (120), (220
) is a receiving circuit, and (140) and (240) are control circuits.

Claims (1)

[Claims] A first and a second transceiver are combined, and a call is made between the first and second transceivers using one of a plurality of call channels. In the transmitting/receiving device, when calling one of the first and second transceivers to the other, searching for an empty channel among the plurality of channels using a predetermined discrimination level, and when an empty channel is obtained through this search. ,
The first and second transceivers are connected through the free channel and communication between the first and second transceivers is permitted, and when no free channel is obtained by the above search, the predetermined discrimination level is searches for an empty channel with a high discrimination level, and when an empty channel is obtained through this search, the first and second transceivers are connected through the empty channel and the communication between the first and second transceivers is performed. A transmitting/receiving device that allows telephone calls.