GB2218595A - Smart socket (mercury) - Google Patents

Abstract

An applique unit for use with a telephone connected to one network (BT) but where access is needed to another network (MCL) monitors the line to detect when the subscriber initiates a call. When he starts to "dial", the telephone is switched to a state in which it is connected to the exchange via the unit. The digits go into store, and are checked as they do so; if they are for a BT call they are sent out in the normal way and the unit drops out to leave the telephone once again connected to the line. If the call is for MCL, there is a pause and the MCL access code is sent, followed by the caller's identity code and the wanted number. In each case sending is in the format appropriate to the network to be used. The criterion for choosing MCL can be either that the wanted line is only accessible via MCL, or that the wanted call would be cheaper via MCL. <IMAGE>

Description

SMART SOCKET (MERCURY) This invention relates to telephone networks and telephone subscribers' apparatus for use where two (or more) separate telephone networks have to interwork.

There are now two circuit switched voice network carriers in the UK, the long-established British Telecom (BT) and the rather newer Mercury Communication Limited (MCL). The licensing arrangements for the two carriers include the provision that interfaces must be provided to enable subscribers on one such carrier to be able to call subscribers on the other carrier. In addition it is useful to be able to set up a call via whichever network gives the cheaper service.

One solution to this problem as described in our Patent Application No. 2171274A also developed for the situation is that calls have to be made from a BT line (or a dual access line) to a MCL line. When such a call has to be made to an MCL line, a second proceed-to-send (dial tone) signal (i.e. a proceed-to-send signal additional to the normal BT signal) is used when access to MCL is needed. For this purpose the subscriber's set includes a detector for the second proceed-to-send signal, but that signal is not heard by the calling subscriber. In that system the wanted number, on "dialling" is placed in a storage device at the calling subscriber's instrument, and if a said second proceed-to-send signal is received that signal is not heard by the caller.However, the reception of that second proceed-to-send signal automatically causes the transmission of an access code appropriate to MCL, whereafter the wanted number and any other information needed, such as the MCL authorisation code, are sent without any further action by the caller, and, as already mentioned, without him hearing the second proceed-to-send signal. The fact that the wanted number is placed in store enables it to be simply 're-dialled" later in response to a repeat code.

A somewhat different approach to the same problem, also for the case where the two systems are BT and MCL is described in Patent Application No. 2192768A (Plessey). In that case a network access device is interposed between the subscriber's instrument and the line to a BT exchange is used. This device includes means for generating signals appropriate to BT, and upon connections to MCL for generating signals appropriate to MCL and also for automatically sending user identity/security data to the MCL network. In this case, establishing the connections to the MCL network needs the operation of a special key to initiate the operations referred to.

An object of this invention is to produce an arrangement for use at a telephone subscriber's instrument better that the arrangements described briefly above.

According to the invention there is provided a network access arrangement for use in conjunction with a telephone subscriber's instrument connected to a telephone exchange of a first telecommunication network, which includes means for monitoring the line outgoing from the instrument to detect outgoing "dialled" digits from that instrument, switching means responsive to the detection by said monitoring means of the commencement of "dialling" therefrom to connect the network access arrangement between the line and the instrument, storage means in said arrangement into which digits from the instrument can pass, further monitoring means for checking those digits to ascertain whether they relate to a call via the first network or via a second telecommunication network, first signalling means responsive to an indication that the call is to be set up via the first network to cause the digits of the wanted number to be sent in the manner appropriate to that first network, whereafter the access arrangement is switched out of circuit and the instrument reverts to its condition in which it is directly connected to the line, and second signalling means responsive to an indication that the call is to be set up via the second network to cause access and any security information appropriate to the second network to be transmitted from the arrangement, followed by the digits of the wanted number, the latter being sent in a manner appropriate to the second network, whereafter the access arrangement is switched out and the instrument reverts to its condition in which it is directly connected to the line.

In the arrangement specified in the preceeding paragraph, the intervention of the network acess arrangement is effected automatically when the caller commences to dial. The wanted number digits then enter a storage device in the access arrangement, and the 'dialled' digits, or at least the earliest digits of the wanted number are monitored.

In the above paragraphs, and in the claims, the word "dialled" is in inverted commas to show that it embraces both conventional dialling and digit sending, from push button sets.

An embodiment of the invention will now be described with reference to the accompanying highly schematic drawing, which relates to an interface device for use between a BT line and a telephone, and which routes calls to the MCL network when it is cheaper to do so.

The arrangement to be described is a device which is connected between the BT line and a telephone, and routes calls to the MCL network when it is cheaper to do so. It is housed in a standard box, which is double the size of an ordinary dual BT telephone socket. The unit has four telephone connector inlets, one of which connects the box to the line, while the others provide three possible telephone extensions. The device is designed with the residential market in mind, and therefore price and ease of use are of great importance.

In an idle state, see the drawing, the telephone is connected to the line via contacts RL1 and RL2 of relays (not shown). The device monitors the line conditions under control of a microprocessor 1 using a serial-connected loop detection circuit 2. When an off-hook- condition and the leading edge of the first dialled digit have been detected by the circuit 2, the line is switched to the device, since the processor 1 then controls the relay driver 3 to set up the relays to the condition in which the contacts are set as shown.

The telephone during the signalling is powered from the external power supply indicated at the lower left-hand corner, and the exchange is kept seized from the device by blocks 4 and 5.

All dialled digits (LD or DTMF) from the caller, one of the lines indicated at 6, are decoded, the number is processed, and redialled to the exchange unmodified for BT calls or modified with the MCL protocol, for Mercury calls.

The software for the processor 1 has to differentiate the line conditions and determine whether or not to switch back to the telephone. Also it should switch back to the telephone during the last inter-digital pause, after the last digit in store has been dialled. This will allow the user to monitor the call progress.

The device will be required to signal in,LD (loop disconnect), DTMF (dual tone MF) or a mixture of the two depending on the BT exchange.

A look-up table will be stored in an EEPROM 7 which could have a default data base installed, and could be directly modifiable from the line. The data from that table is passed in DTMF tones, and involves the user calling a remote database number.

The unit is mains powered, as already indicated, by a mains socket power supply. All controlled signals are opto-isolated from the telephony side of the device. The output of the power supply unit is floating also the mains transformer will provide a safety barrier to the network.

We now consider the mode of operation of the device.

Incoming Call In the idle state the relays RL1, RL2 (not shown) are switched to the telephone side which is the reverse of the condition of the contacts shown. Ringing is detected by the called telephone but no action is taken by the access device. When the call is answered, when the subscriber goes off hook, again no action is taken by the device because the detection of the ringing signal was noted, and indicated that no action is needed.

BT Call The user lifts the handset and dials the required number. The device detects the off-hook condition and awaits the first dialled digit, so that the caller can hear dial tone. The leading edge of the first dialled digit will be detected, and the line is switched to the device, via the processor 1 and the relay driver 3.

The telephone is now powered from the external PSU and all the dialled digits are detected in a DTMF transceiver 8, or by the loop detection device 2, if the dialling uses loop detection. They are then stored and examined by the processor 1. The processor determines that it is a local call, causes redial of the number.

During the inter-digital pause, and if all the stored digits have been dialled, the line is switched back to the telephone. This occurs under processor control.

Any further digits entered by the user will be allowed to be dialled to the exchange directly. No further action is taken by the device.

Mercury Call The user lifts the handset and dials the required number. The device detects the off-hook condition and awaits the first dialled digit. Once again this allows the user to hear the dial tone. The leading edge of the first dialled digit will be detected and the line is switched to the device, as happened for the BT call.

The telephone is now powered from the external PSU and all the dialled digits are detected, stored and examined. The device determine from the first four digits that it should be a Mercury routed number, or, under processor control, that it is a call whose establishment would be cheaper via Mercury. The Mercury access code, 131, is first dialled automatically, under control of the processor 1 and via the transmission circuit 5. Then a delay of fixed/programmable time is inserted. After that the user's authorisation code will be sent in DTMF. When no more digits are detected, then the line will be switched back to the telephone.

After the line is switched to the telephone, if any further digits are entered, possibly because the user is very slow to complete the dialled number, those digits will be detected and redialled after the line is switched to the device.

The time taken for a Mercury call setup is longer than a BT call but this is not likely to cause any trouble.

Call Clearing Once the handset has been replaced the device will detect this condition and revert to the idle state.

Although the device described above is a unit separate from but associated with the telephone instrument, it will be appreciated that it could be incorporated into the telephone instrument. This could be advantageous where the instrument is a so-called 'facilities' set with a microprocessor, since this additional function would enable the microprocessor to be more fully employed.

Although we have described the invention as applied to the British situation with BT and MCL, it will be understood that it can also be used in other cases where two or more networks have to interwork.

Claims (4)

CLAIMS:

1. A network access arrangement for use in conjunction with a telephone subscriber's instrument connected to a telephone exchange of a first telecommunication network, which includes means for monitoring the line outgoing from the instrument to detect outgoing 'dialled' digits from that instrument, switching means responsive to the detection by said monitoring means of the commencement of "dialling" therefrom to connect the network access arrangement between the line and the instrument, storage means in said arrangement into which digits from the instrument can pass, further monitoring means for checking those digits to ascertain whether they relate to a call via the first network or via a second telecommunication network, first signalling means responsive to an indication that the call is to be set up via the first network to cause the digits of the wanted number to be sent in the manner appropriate to that first network, whereafter the access arrangement is switched out of circuit and the instrument reverts to its condition in which it is directly connected to the line, and second signalling means responsive to an indication that the call is to be set up via the second network to cause access and any security information appropriate to the second network to be transmitted from the arrangement, followed by the digits of the wanted number, the latter being sent in a manner appropriate to the second network, whereafter the access arrangement is switched out and the instrument reverts to its condition in which it is directly connected to the line.

2. An arrangement as claimed in claim 1, in which the arrangement is a separate unit from the telephone subscriber's instrument with which it is associated, but is connected thereto.

3. An arrangement as claimed in claim 1, in which the arrangement is incorporated into a telephone subscriber's instrument.

4. A network access arrangement, substantially as described with reference to the accompanying drawings.