GB2382951A

GB2382951A - Telephone line selection apparatus

Info

Publication number: GB2382951A
Application number: GB0228060A
Authority: GB
Inventors: Du Le-Ngoc
Original assignee: GBD COMM Ltd
Current assignee: GBD COMM Ltd
Priority date: 2001-12-03
Filing date: 2002-12-02
Publication date: 2003-06-11
Also published as: GB0128890D0; GB0228060D0

Abstract

A line-powered telephone system having two lines so that a handset can be connected to the first line and another handset or a laptop computer to the other. A circuit is provided so that if one line is being used and there is a power failure on that line, the handset or laptop being used is automatically connected to the other line. Also disclosed is a multi-line, line-powered telephone system having a circuit with a relay which enables a user to select one of the lines available solely utilising power provided by the telephone line, operation of the relay being solely dependent on the telephone line power.

Description

Title: Telephone Line Selection Apparatus The present invention relates to telephones and more particularly, but not solely, to telephone line selection.

In hotels, in particular, it is now desirable to have two telephone lines to a room. The telephone handset may be latched onto one"first"line whilst the user connects a laptop computer to the other"second"line. The user may wish to leave the first line free for incoming calls whilst using the second line to make an outgoing call. In line-powered systems the telephone handset is normally latched onto the first line, but if the first line is"down", i. e. not working, the handset does not or cannot switch to the second line and it therefore becomes inoperable.

According to the present invention there is provided a multi-line, line-powered telephone system in which the handset of the telephone system is connected to one powered line and a circuit is provided which connects the handset automatically to another line in the event of power failure in said one line.

A constructional embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing which shows a circuit according to the invention.

Historically, latching mechanical switches are used to select a line. This proves to be convenient when an in-coming call is on the line not being selected. The circuit shown has a low-powered latching relay to select or automatically select a line. When current flows through the coil in one direction one line is selected.

When it flows in the opposite direction, the other line is selected. Once a line is selected, it remains selected with or without current through the coil unless :

1. A user manually selects the other line ; 2. A user answers a call after the other line rings.

When there is an in-coming call, the phone always selects the line that rings. This feature is available when the phone is idle. When it is in use, this feature is disabled since the phone is under the control of the user. When the user makes an out-going call, the phone automatically selects the last line in use.

In the circuit :- LINEIJTIP is the tip of the first PSTN or PBX extension LINE1 RING is the ring of the first PSTN or PBX extension LINE2 - TIP is the tip of the second PSTN or PBX extension LINE1 RING is the ring or the second PSTN of PBX extension LINE1 RINGER is a positive DC voltage that represents in-coming call on line 1.

This voltage may be coverted to another level for correct interfacing.

LINE2~RINGER is a positive DC voltage that represents in-coming call on line 2.

This voltage may be coverted to another level for correct interfacing.

POSITIVE is the positive connection the speech circuit, dialler circuit and/or microcontroller.

NEGATIVE is the negative connection the speech circuit, dialler circuit and/or microcontroller.

LINE1 is a positive control signal to switch relay to the first PSTN line or PBX extension. For example, it could be a logic signal from a microcontroller.

LINE2 is a positive control signal to switch relay to the second PSTN line or PBX extension. For example, it could be a logic signal from a microcontroller.

For transistors, 01, Q2, 03 and Q4, P and N channel FET transistors could be used.

2 coil latching relay could be used which will allow users to manually select the line. If one of the two lines is not connected to PSTN or PBX extension, this line will not be selected since there is NO POWER on that line.

In a system according to the present invention in a system having two lines to one telephone handset, the handset is connected to the first line by default, If a user specifically wishes to switch over to the second line it is possible to do so by depressing a key, button or pad. However, if the first line loses power the system will automatically switch to the second line.

The telephone line selection circuit is a circuit design based on relay that enables the users to select one of the lines available solely utilising power provided by the telephone line. The relay is used in this design in order to provide physical isolation between the telephone lines which leads to minimum cross-talk. The circuit has also been designed in such a way that the operation of the relay is totally dependent on the telephone line power which means a line can not be selected unless it is in working conditions.

Figure 2 of the drawings will now be described.

The circuit description is provided for a two-line telephony equipment which best demonstrates the idea. In theory, the idea can apply to multi-line telephony products.

Each telephone line consists of 3 parts: ring detection circuit, relay activation circuit and relay circuit.

For line 1, capacitor Cl, resistors Rl, R2, bridge D1, zener D2 and opto-isolator ISOl form the ring detection circuit. The output ofISOl, LINE1~RING provides a ring detection signal that would facilitate the automatic line selection upon receipt of in- coming ring signal.

Bridge D3 ensures the telephone line DC voltage to the relay activation circuit would be of a constant polarity. The relay activation circuit consists of diodes D4, D5, transistor Q1, resistors R3, R4, switch LINE1-KEY, capacitor C2. LINE1 can be selected by the users by pressing LINE1~KEY switch OR it can be automatically selected by applying a correct signal to LINEI-SELECT. LINE I-RELAY-signal can be used with an appropriate interface circuit to indicate the line selected.

For line 2, capacitor C3, resistors R5, R6, bridge D6, zener D7 and opto-isolator IS02 form the ring detection circuit. The output of IS02, LINE2 ~RING, provides a ring detection signal that would facilitate the automatic line selection upon receipt of in- coming ring signal.

Bridge D8 ensures the telephone line DC voltage to the relay activation circuit would be of a constant polarity. The relay activation circuit consists of diodes D9, DIG, transistor Q2, resistors R7, R8, switch LINE2-KEY, capacitor C3. LINE2 can be selected by the users by pressing LINE2~KEY switch OR it can be automatically selected by applying a correct signal to LINE2 ~SELECT. LINE2 - RELAY - signal can be used with an appropriate interface circuit to indicate the line selected.

The above two telephones lines can be selected and connected to other parts of the complete telephony system by means of K1 relay contacts.

Claims

CLAIMS:

1. A multi-line, line-powered telephone system in which a handset of the telephone system is connected to one powered line and a circuit is provided which connects the handset automatically to another line in the event of power failure in said one line.

2. A telephone system as claimed in claim 1, having two lines, wherein the circuit has a low-powered latching relay for line selection, the relay having a coil whereby when current flows through the coil in one direction one line is selected and when current flows in the opposite direction the other line is selected.

3. A telephone system as claimed in claim 1 wherein the circuit is substantially as described with reference to and as illustrated by the Figure 1 of the accompanying drawings.

4. A multi-line, line-powered telephone system having a circuit with a relay which enables a user to select one of the lines available solely utilising power provided by the telephone line, operation of the relay being solely dependent on the telephone line power.

5. A telephone system as claimed in claim 4 and substantially as described with reference to and as illustrated by the Figure 2 of the accompanying drawings.