Interconnection control method in cordless telephone system

Details Interconnection control method in cordless telephone system Interconnection control method in cordless telephone system

1988-10-18

1991-02-05

Ng, Jin F.

Telephonic communications

Audio message storage, retrieval, or synthesis

379 61, H04M 1100

Patent

active

049911988

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an interconnection control method in a cordless telephone system which comprises a connection unit and a plurality of wireless or radio telephone sets.


BACKGROUND ART

An example of such a sort of prior art cordless telephone systems is shown in FIG. 6. In the drawing, the system comprises a connection unit 10 which is connected to a subscriber line 2 of an exchange 1 in a central office and which includes a hybrid circuit 11 performing two-wire/four-wire conversion, a transmitter 12, a receiver 13, a control circuit 14 and an identification information memory 15. The system also comprises a radio telephone set 20 which is connected through a radio communication circuit to the connection unit 10 and which includes a transmitter 22, a receiver 23, a control circuit 24, an identification information memory 25, a key switch unit 26, a handset receiver 28 and a handset transmitter 28.
In such an arrangement, when an operator of the radio telephone set 20 depresses a calling key in the key switch unit 26 to made a call, information indicative of the call request is transferred to the control circuit 24. The circuit 24, when receiving the information, drives the transmitter 22 to transmit, in the form of radio waves on a control channel, a calling signal which comprises a bit synchronization signal, a frame synchronization signal and subsequently an identification code (ID code) unique to the radio telephone set 20, as shown in FIG. 7 (a).
The connection unit 10, when receiving the identification code of the radio telephone set 20 which forms a pair with the unit 10 on the control channel, transmits, from the transmitter 12 in the form of radio waves on the control channel, a calling answer signal which comprises a bit synchronization signal, a frame synchronization signal, and subsequently a speech channel assignment code and the identification code of the telephone 20, as shown in FIG. 7(b).
When the radio telephone set 20 receives the calling answer signal at the receiver 23, the control circuit 24 switches the speech channel to the one assigned by the received answer signal. The connection unit 10 itself, on the other hand, switches the speech channel to the one assigned by its own. And after the connection unit 10 has confirmed that the switched channel is idle, the unit establishes a DC closed loop between the hybrid circuit 11 and the exchange 1, modulates a dial tone transmitted through the DC closed loop from the exchange 1 and then transmits the modulated dial tone from the transmitter 12 to the radio telephone set 20. On the side of the telephone 20, when the receiver 23 receives this dial tone, the tone is sounded at the handset receiver 27.
At this stage, operator's dial-number dialling operation on the side of the radio telephone set 20 causes the dial number to be transmitted through the radio communication circuit and the connection unit 10 toward the exchange 1. The transmission completion of the dial number causes the connection exchanging operation of the exchange 1, thus calling the party subscriber line. As a result, if the party subscriber answers the call, then the system is put in the speech mode.
When the operator of the radio telephone set 20 wants to terminate his conversation, he returns the calling key of the telephone to the initial position to put the telephone in an on-hook mode. This causes the on-hook signal to be transmitted to the connection unit 10. When a predetermined constant time has elapsed after the transmission of the on-hook signal, the radio telephone set 20 also transmits a speech end signal to the connection unit 10. The unit 10, when receiving the speech end signal, `opens` the DC loop between the exchange 1 and the unit to release the subscriber line 2.
When the connection unit 10 receives a call from the subscriber line 2 in an await mode, the control circuit 14 of the unit 10 detects a calling signal received from the exchange 1 to transmit through the control channel of the transmitter 12 a call indicator sig

REFERENCES:
patent: 4646345 (1987-02-01), Zdunek et al.
patent: 4679225 (1987-07-01), Higashiyama
patent: 4776001 (1988-10-01), Murata et al.

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