Multi-channel access (MCA) radio telephone system

Claim 2

A multi-channel access radio telephone system for carrying calls with a plurality of radio channels shared by a combination of a base station coupled to a first telephone set, and a plurality of substations connected to a second telephone set, said multi-channel access radio telephone system including a clearing method comprising the steps of: a) detecting the hanging-up of said first telephone set; b) maintaining the direct current loop of the subscriber line of said first telephone set in response to this detection of the hung-up state and returning said radio channel to a waiting state; c) detecting the hanging-up of said second telephone set and again establishing a radio channel between said base station and said substation; d) sending through the re-established radio channel a release signal from said substation to said base station; and e) opening said direct current loop in response to said release signal and placing said re-established radio channel into a waiting state.

Claim 3

A multi-channel access radio telephone system, as claimed in Claim 1, wherein the detection of the hanging-up of said first telephone set is achieved with the busy tone sent from the side of said first telephone set.

Claim 4

A multi-channel access radio telephone system, as claimed in Claim 1, wherein said Step b) includes the steps of; ' bl) maintaining said direct current loop in response to the detection of the hanging-up of said first telephone set and sending a disconnection signal to said substation; b2) placing the transmission from said base station into a waiting state after sending said disconnection signal; and b3) generating a local busy tone at said substation in response to said disconnection signal and turning off the transmission from said substation.

Claim 5

A multi-channel access radio telephone system, as claimed in Claim 1, wherein said Step e) includes the steps of; el) maintaining said direct current loop in response to the detection of the hanging-up of said first telephone set and sending a line-lock disconnection signal to said substation; b2) placing the transmission from said base station into a waiting state after sending said disconnection signal; and b3) turning off the transmission from said substation in response to said line-lock disconnection signal.

Claim 6

A multi-channel access radio telephone system, as claimed in Claim 1, wherein Step c) includes the steps of; cl) detecting the hanging-up of said second telephone set and sending a call origination signal to said base station over a radio channel where an idle signal is present; c2) turning off said idle signal in response to said call origination signal; c3) sending, in response to the turning-off of said idle signal, the identification number signal of said substation over said radio channel from said substation to said base station; c4) returning said identification number signal over said radio channel from said base station to said substation; and c5) completing the formation of a radio channel by the reception of the returned identification number signal by said substation.

Claim 7

A multi-channel access radio telephone system having an exchange accommodating a plurality of telephone sets; a base station coupled to said exchange by way of a plurality of first subscriber lines; substations each connected to said base station via one of a plurality of radio channels and having at least one telephone set; and a plurality of subscriber circuits coupled between said exchange and said base station and respectively accommodating one of said first subscriber lines, each of said subscriber circuits having a busy tone detector for detecting a busy tone from the corresponding one of said first subscriber lines and a terminating circuit for forming a direct current loop by terminating said corresponding first subscriber line, wherein: after the completion of conversation between a first one of the plurality of telephone sets accommodated in said exchange and a second one among the telephone sets of said substations, when said first telephone set is hung up first, this hanging-up is detected by said busy tone detector; said direct current loop is maintained by terminating said first subscriber line concerning with said first telephone set with said terminating circuit; a radio channel between said base station and said substation is released; and when said second telephone set is hung up after this release, a radio channel is again established between said base station and said substation; said substation sends a release signal over this re-established radio channel to the subscriber circuit concerning with said first telephone set; said direct current loop is opened by said terminatin q circuit in response to said release signal, and said re-established radio channel is released.

Claim 8

A multi-channel access radio telephone system having an exchange accommodating a plurality of telephone sets; a base station coupled to said exchange by way of a plurality of first subscriber lines; substations each connected to said base station via one of a plurality of radio channels and having at least one telephone set; and a plurality of subscriber circuits coupled between said exchange and said base station and respectively accommodating one of said first subscriber lines, each of said subscriber circuits having a busy tone detector for detecting a busy tone from the corresponding one of said first subscriber lines and a terminating circuit for forming a direct current loop by terminating said corresponding first subscriber line, wherein: after the completion of conversation between a first one of the plurality of telephone sets accommodated in said exchange and a second one among the telephone sets of said substations, when said first telephone set is hung up first, this hanging-up is detected by said busy tone detector; said direct current loop is maintained by terminating said first subscriber line concerning with said first telephone set with said terminating circuit; a radio channel between said base station and said substation is released; and when said second telephone set is hung up after this release, a radio channel is again established between said base station and said substation; said substation sends a release signal over this re-established radio channel to the subscriber circuit concerning with said first telephone set; said direct current loop is opened by said terminatin q circuit in response to said release signal, and said re-established radio channel is released.

Claim 9

A multi-channel access radio telephone system, as claimed in Claim 6, wherein said radio channel is released by the sending of a disconnection signal from said substation to said base station in response to the detection of the hanging-up of said first telephone set to cease the transmission of said base station, and further to cease the transmission of said substation in response to said disconnection signal.

Claim 10

A multi-channel access radio telephone system, as claimed in Claim 7, wherein said substation supplies a local busy tone to said second telephone set in response to said disconnection signal.

Claim 11

A multi-channel access radio telephone system, as claimed in Claim 6, wherein said subscriber circuit is placed in a concentrator arranged between said exchange and said base station, and said first subscriber lines comprise n pairs of subscriber lines between said exchange and said concentrator and m pairs of subscriber lines between said concentrator and said base station, said n and m being positive integers and n being greater than m.