AU666764B2 - Alert method for cordless telephones - Google Patents

Description

-1F1- ALERT METHOD FOR CORDLESS TELEPHONES Field of the Invention The present invention relates generally to the field of communications and particularly to cordless telephones.

Background of the Invention e 0 .1 0 An obvious requirement of any telephone is that it must ring or generate some form of alert tone. Ringing in a landline telephone is initiated by a ring voltage that is turned on and off by the telephone company. A typical ring is a cycle of two seconds on and four seconds off. Some telephone 1 5 systems support distinctive ringing. A distinctive ring is defined as one short-long-short ring cycle every six seconds as specified in the Bellcore document CLASSSM Feature Distinctive Ringing/Call Waiting, TR-TSY-000219 Issue 2, Revision 1. The two short rings are 200 to 500 ms in length and the one long ring is 800 to 1000 ms. The off periods between the long and short rings are 200 to 500 ms in duration. An off period after the last short ring is for the remainder of the six second cycle. It is typically desirable that the ringing of all phones at 25 a particular number be synchronized. Unsynchronized ringing sounds strange to the end user. In a cordless telephone, ringing must be initiated by an RF signal from the cordless telephone's base unit.

In order to synchronize ringing in a cordless telephone, 3 0 a message could be sent to start or stop the ring. This solution would not work in a system that transmits data sub-audibly at a low speed since a message could take approximately 700 ms to transmit. The ring duration is much shorter than the time to transmit a message.

Another solution would be to dedicate several bits in the message for a ring indication. These ring indication bits would be evenly distributed throughout the message. After -2seeing a predetermined number of these bits in the ringer ON state, the handset would begin ringing. A predetermined number of these bits in the ringer OFF state would indicate to the handset that it should terminate ringing.

In this case, the handset needs to sample several bits prior to changing the ring state to avoid falsing. If the handset needed to receive two bits in the ringer ON state prior to turning on the ringer, and if the ringer must be turned on °o o within 100 ms of the land line indication, then the base would o00 1 0 need to transmit at least two ring indication bits every 100 ms.

o0oo Ring indication bits, therefore, would consume 20 percent of ao the message stream in a cordless system that transmits 100 Manchester bits per second. Dedicating 20 percent of the .0000 message stream to the ring indication severely diminishes the throughput of the communications channel for other operations. There is a resulting need for an alert control Smethod that does not require dedication of a significant 0 0" portion of the message stream.

j-y of thC Ivfnion i 00 0 The process of the present invention encompass method for controlling an alert tone in a cordl elephone. 00 The cordless telephone is comprised ofase unit, a handsetj o( 00 25 unit, and an alert generator. T ethod begins by the base unit detecting a ring si If the ring signal is detected, the base unit trans ts an alert start message and a tone signal Sto the hdset unit. If the handset unit receives the tone Ssigal and the alert start message, the alert generator is k 7r -2a- Summary of the Invention According to one aspect of the present invention there is provided a method for controlling an alert tone in a cordless telephone having a base unit, a handset unit, and an alert generator, the method including the steps of: the base unit detecting a ring signal; when the ring signal is detected, the base unit transmitting an alert start message to the handset unit; when the ring signal is detected, the base unit transmitting a tone signal to the handset unit; and after the handset unit receives the alert start message, activating the alert generator when the handset receives the tone signal.

According to a further aspect of the present invention there is provided a method for controlling an alert tone in a cordless telephone having a base unit, a handset unit, and an alert generator, the base unit communicating with the handset unit via an audible voice band and a sub-audible data band, the method including the steps of: the base unit detecting a ring signal; when the ring signal is detected, the base unit transmitting an alert start message in the sub-audible data band to the handset unit; Swhen the ring signal is detected, the base unit transmitting a tone signal in I the audible voice band to the handset unit; after the handset unit receives the alert start message, activating the alert generator when the handset received the tone signal; and when the handset unit receives an alert stop message, deactivating the alert generator.

According to a still further aspect of the present invention there is provided a method for controlling an alert tone in a cordless telephone having a base unit, a handset unit, and an alert generator, the base unit communicating with the handset via an audible voice band and a sub-audible data band, the method including the steps of: 3 Wthe base unit detecting a ring signal; MJP C:\WINWORD\MARIE\GABNODEL\47412C.DOC -2bwhen the ring signal is detected, the base unit transmitting an alert start message in the sub-audible data band to the handset unit; when the ring signal is detected, the base unit transmitting a tone signal in the audible voice band to the handset unit; updating an energy total upon the alert start message and the tone signal; when the energy total is greater than or equal to a predetermined threshold, activating the alert generator; and when the handset unit receives an alert stop message, deactivating the alert generator.

According to a still further aspect of the present invention there is provided a cordless telephone for communicating with a land-line telephone system, the telephone including: alert generation means; a base unit coupled to the land-line telephone system and receiving a ring signal from the land-line telephone system; a handset unit for communicating with the base unit over sub-audible and audible portions of a communication channel, the handset unit having processing means for performing a method for alert control in response to the ring signal, the method including the steps of: the base unit detecting the ring signal; when the ring signal is detected, the base unit transmitting an alert start message to the handset unit; when the ring signal is detected, the base unit transmitting a tone signal to the handset unit; and when the handset unit receives the alert start message, activating the alert generator when the handset receives the tone signal.

MJP C:\WINWORD\MARIE\GABNODEL47412C.DOC -3- Brief Description of the Drawings FIG. 1 shows a flowchart of the process of the present invention.

FIG. 2 shows the signals generated in accordance with the process of the present invention.

FIG. 3 shows a simple block diagram of a cordless telephone in accordance with the present invention.

oo 0 0 0 O 0o 0 0 o000 a 0 0o 0000 0000 0 0 3 0000 00 o *00 0 Co 0 00 0 0 000 000000 0 0 Detailed Description of the Preferred Embodiment A cordless telephone base unit, using the process of the present invention, transmits a sub-audible alert or ring start and stop message to the handset unit. After the ring start is 1 5 transmitted, a tone is transmitted to signal the ring to start.

As a result, after a slight delay to receive the initial message, the handset rings in cadence with other extension telephones at the particular number being called.

The process of the present invention, illustrated in FIG.

1, begins when the handset locks to the base unit (201). This locking operation occurs when the base unit transmits a narrowband pattern to the handset so that the handset locks to the channels assigned to cordless telephones. The handset's alert generator is also turned off in case it was previously 25 turned on (203). A RING_TOTAL value is initialized to zero at this point. RING_TOTAL contains a running total of the energy detected on the c] lannel. The energy level is high when the tone is turned on and is low when the tone is turned off.

3 0 The process then continuously checks the sub-audible data message stream for a ring start message (205) sent by the base unit. This message is one of many messages that the base can transmit to the handset unit. After receiving this message, the handset monitors the audible portion of the 3 5 channel (206). The handset next determines if the ring stop message was received (207). If the ring stop message was -4received, the handset turns off the ringer and resets RING_TOTAL (203).

If the ring stop message was not received, the most recent low speed data bit received from the base unit is examined to determine if it is in error (209). This error check avoids falsing under poor signalling conditions. Ideally, it also avoids falsing on voice in the event of co-channel interference. The process of the present invention provides °o hysteresis to prevent falsing and bit error determination to 1 0 detect erroneous samples. In an alternate embodiment, a 00° severe shift in the received signal strength indicator (RSSI) 0000 oo could also be utilized to detect erroneous samples.

o o o If the BER indicates that the most recent bit is in error 0000 0 (211), the process branches to (207). The audible portion of the 1 5 channel is not sampled if the bit is in error. This is done since an error in sub-audible data indicates that the sample of the 0 audible band is probably in error.

SIf the sub-audible data bit is not in error (211), the 0° audible portion of the channel is measured to detect for the 2 0 presence of a tone (213). This measurement is done via an 00 0 o expander A/D conversion. This sample is combined into RING_TOTAL (215) by the equation: RING TOT* 2 0 o RING TOT =N TONE_DET.

o, 0 0 3 0 This method of updating RINGTOT provides the hysteresis to prevent falsing.

RING_TOT is now compared to a RING_THRESH (217). RING_THRESH is picked so that it is as high as possible to avoid falsing on noise but also low enough so that a small number of samples will cause the threshold to be exceeded. In the prefe Ted embodiment, RING_THRESH is 104. In this embodiment, the expander A/D samples are approximately 40 when the base is transmitting the tone.

3 5 If RINGTOT meets or Pycoeds RING_THRESH, then the ringer is turned on (221). In an alternate embodiment, the L. ringer is checked before it is turned on to avoid a strange sounding alert. If RINGTOT is less than RINGTHRESH, then the ringer is turned off (219).

Whether the ringer is turned on or off, the process continues by checking for a ring stop message (207). A message that indicates that ringing should be terminated is sent sub-audibly by the base once the call is answered or the land-line ringing stops for ten continuous seconds. Once this 00 o message is received, the ringer is turned off and RING_TOT 10 reset (203).

FIG. 2 illustrates the audible (401) and sub-audible (402) portions of the communication channel. The -ring start signal (403) is present on the sub-audible (402) band and the tone (404) is present on the audible (401). In the preferred embodiment, the ring stop signal (405) occurs ten seconds after the last tone.

In an alternate embodiment, the ring start signal (403) can occur mulitple times before the ring stop signal (405). Also in this embodiment, the ring stop signal (405) may be 8transmitted multiple times after the last tone (404).

FIG. 3 illustrates a simple block diagram of a typical cordless telephone using the process of the present invention.

The base unit (301) is connected to the land-line telephone system from which it receives the ring signal. The handset 2 (302) is comprised of a transceiver (303) to transmit and 25 receive signals. The transceiver (303) is connected to audio o i~ circuits (305) that contain the A/D converter and the ring 1i generation circuits. An interface circuit (311) performs the signalling for the handset. A microprocessor (307), in l conjunction with he memory (309), controls the operation of the handset and uses the process of the present invention.

e 1-i I

Claims (7)

1. A method for controlling an alert tone in a cordless telephone having a base unit, a handset unit, and an alert generator, the method including the steps of: the base unit detecting a ring signal; when the ring signal is detected, the base unit transmitting an alert start message to the handset unit; when the ring signal is detected, the base unit transmitting a tone signal to the handset unit; and after the handset unit receives the alert start message, activating the alert generator when the handset receives the tone signal.

2. The method of claim 1 and further including the step of when an alert stop \message is received by the handset unit, deactivating the alert generator. 15

3. A method for controlling an alert tone in a cordless telephone having a .o base unit, a handset unit, and an alert generator, the base unit communicating with the handset unit via an audible voice band and a sub-audible data band, the method including the 5teps of: I the base unit detecting a ring signal; when the ring signal is detected, the base unit transmitting an alert start message in the sub-audible data band to the handset unit; when the ring signal is detected, the base unit transmitting a tone signal in the audible voice band to the handset unit; after the handset unit receives the alert start messag activating the alert generator when the handset received the tone signal; and when the handset unit receives an alert stop message, deactivating the alert generator.

4. A method for controlling an alert tone in a cordless telephone having a base unit, a handset unit, and an alert generator, the base unit communicating with the handset via an audible voice band and a sub-audible dpta band, the method including the steps of: the base unit detecting a ring signal; i MJP C:WINWORC ARIEGABNUDEL47412C.DOC L 0 T- -7- when the ring signal is detected, the base unit transmitting an alert start message in the sub-audible data band to the handset unit; when the ring signal is deAected, the base unit transmitting a tone signal in the audible voice band to the handset unit; updating an energy total upon the alert start message and the tone signal; when the energy total is greater than or equal to a predetermined threshold, activating the alert generator; and when the handset unit receives an alert stop message, deactivating the alert generator.

5. A cordless telephone for communicating with a land-line telephone system, the telephone including: alert generation means; a base unit coupled to the land-line telephone system and receiving a ring signal from the land-line telephone system; a handset unit for communicating with the base unit over sub-audible and i audible portions of a communication channel, the handset unit having processing means for performing a method for alert control in response to the ring signal, the Smethod including the steps of: ii: the base unit detecting the ring signal; i when the ring signal is detected, the base unit transmitting an alert start message to the handset unit; when the ring signal is detected, the base unit transmitting a tone signal to 9 the handset unit; and when the handset unit receives the alert start message, activating the alert generator when the handset receives the tone signal.

6. A method for controlling an alert tone in a cordless telephone substantially as herein described with reference to the accompanying drawings.

7. A cordless telephone substantially as herein described with reference to the accompanying drawings. DATED: 17 November, 1995. PHILLIPS ORMONDE FITZPATRICK Attorneys for V da,, I MOTOROLA, INC., MJP C:\WINWORDMARIE\GABNODEI.W7412C.DOC i 1 ALERT METHOD FOR CORDLESS TELEPHONES Abstract of the Disclosure Ai /B The method of the present invention controls the alert generation of a cordless telephone, thus synchronizing all cordless telephones at a particular number. The base unit of 1 5 the cordless telephone sends a ring start message in the sub- audible message stream to the handset unit. The handset then monitors the audible portion of the channel for a tone. Upon reception of the tone, the alert is generated until the handset receives the sub-audible ring stop message from the base unit.