Telecommunications – Transmitter and receiver at same station – Transceiver controlling a separate transceiver or receiver
Patent
1996-04-19
1998-09-01
Urban, Edward F.
Telecommunications
Transmitter and receiver at same station
Transceiver controlling a separate transceiver or receiver
455411, 455517, 455414, 34082544, 367197, H04B 140
Patent
active
058024573
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/Fl 95/00151, filed Mar. 21, 1995.
FIELD OF THE INVENTION
The invention relates to a method for activating ambience listening in which a first mobile radio unit transmits ambient sounds and voice to a second radio unit over a radio path.
BACKGROUND OF THE INVENTION
The invention relates to radio telecommunications systems. A subscriber of a radio telecommunications system, i.e. a radio unit or a subscriber station, such as a mobile phone or some other means of communication, may be registered in a radio network or radio system through system or traffic channels maintained by the base stations of the radio network.
Apart from system channels of radio telecommunications systems, direct mode channels can also be used, i.e. direct mode operation can be applied. Radio units or subscriber stations using direct mode operation do not communicate with a radio network or its base stations. Direct mode channels are frequencies or channels at which mobile phones or other means of communication are able to communicate directly with one another without going through components of the system.
Direct mode channels are typically used in cases where, e.g., a plural number of hand-portable mobile phones communicate with one another at such a distance from the base station that system channels cannot be used.
Another important use of direct mode channels is in the addition of capacity when traffic increases rapidly in one part of the service area of the system, e.g. at one point of the radio network.
A direct mode channel is also called a direct or simplex channel, or a simplex connection. A direct mode channel is a channel that is typically not at all used by the system. It may be, for example, a channel with the same channel spacing as the channels of the system, e.g. 12.5 kHz or 25 kHz. Of the mobile phones operating on the direct mode channel, the transmitting station has tuned its transmitter to the channel and transmits speech or data information. The other mobile phones set to direct mode operation have tuned their receivers to the same channel, whereby they are able to directly hear the transmission.
On a direct mode channel, both analog modulation and digital modulation can be used. The mobile phone transmitting on the channel can also send signalling information, such as information about access rights and priorities or a group operating on the channel. On a direct mode channel, messages can be encrypted, or speech can be transmitted in clear form.
Radio units, i.e. subscriber stations, operating in direct mode communicate with other radio units on a direct mode channel, without necessarily being in direct contact with the base stations of the radio network.
In private mobile radio systems PMR, it is conventional to use an ambience listening function, in which the speech paths of a radio unit, such as a mobile phone, are opened and the transmitter is activated without any indication to the user interface of the mobile phone. In prior art solutions, it has been possible to activate ambience listening either from the mobile phone listened to or through the system from another terminal equipment. When the ambience listening function is activated from the mobile phone listened to, the call is forwarded to a predetermined number, usually to a dispatcher or a station on duty.
The direct mode channels of the prior art operate on a so-called open channel principle. This means that a mobile station can call another mobile station or other mobile stations using selective calls. Actual signalling is not used in the prior art systems.
On a direct mode channel of the prior art, ambience listening has not been realized. It has been impossible to activate the ambience listening function from another mobile phone that operates on the direct mode channel. Yet this would be an important characteristic precisely in the PMR systems, since PMR systems are often used by the authorities, e.g. by the police and in rescue operations, where it is of great advantage if a ra
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patent: 4060803 (1977-11-01), Ashworth, Jr.
patent: 4640987 (1987-02-01), Tsukada et al.
patent: 5239294 (1993-08-01), Flanders et al.
patent: 5384847 (1995-01-01), Hendrickson et al.
patent: 5400011 (1995-03-01), Sutton
Heiskari Mika
Lehmusto Mika
Armstrong Darnell R.
Nokia Telecommunications Oy
Urban Edward F.
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