WO1998047416A1

WO1998047416A1 - Mail box system

Info

Publication number: WO1998047416A1
Application number: PCT/SE1998/000700
Authority: WO
Inventors: Kjell Eriksson; Jan Liesen
Original assignee: J.K. Clearlock Hb
Priority date: 1997-04-23
Filing date: 1998-04-17
Publication date: 1998-10-29
Also published as: NO995151D0; SE9701532D0; SE9701532L; SE512232C2; NO995151L; EP0979052A2

Abstract

The invention relates to a system for verifiable clearing of mail boxes (2) wherein the respective mail box (2) is registered together with the clearing time. The respective mail box (2) is registered as an individual and is opened with a mixture of electronic identification together with mechanical lock (3). After clearing, the information concerning clearing of the mail box (2) is arranged to be presented on a display or in some other manner for a certain appointed time. Thus, the lock (3) for the respective mail box (2) is passive and may only be opened at the adjusted time or during a period around this.

Description

Mail box system

The present invention relates to a system for verifiable actuation of the locks of mail boxes by means of a key.

A prior art system for allowing mail boxes to be cleared comprises a mechanical key by which existing locks for the mail boxes that are desired to be cleared are allowed to be locked up, and which may be performed according to any possible plan at any time and by any holder of a key. This involves disadvantages for persons mailing letters in the boxes, because they can not be sure that the box will be emptied at the intended clearing time or if the box has already been emptied. The main object with the present invention is therefore first of all to provide a system by which said disadvantages are eliminated in a safe and efficient manner.

Said object is achieved by means of a system according to the present invention, which is primarily characterized in that there is a display on the aforementioned mail box or in its immediate vicinity which is arranged to show information about clearing of the mail box only during a certain time after performed clearing, that for each one of said mail boxes which are parts of said system for clearing there is a lock unit which is mechanical arranged to be programmed with a unique individual number which is unique for each respective mail box lock, that the information about the point of time of clearing of mail boxes and their identity code is arranged to be stored within the key for clearing, wherein for clearing the mail boxes which are a part of the programmed clearing route for each key, the current appointed box is arranged to identify itself by means of the key for clearing and after approved identifying of the individual and time within the interval for clearing, the key for clearing code is transmitted to the lock unit for electrical activation of the lock catch and the lock is arranged to be opened for clearing the box and for subsequent activation of the clearing display of the box but to send code for deactivating the lock unit in case of inadmissible criterion of clearing.

By having an earliest allowable opening time in the key, the box can not be emptied before the stipulated time posted on the box. If the clearer one day would be hurrying to rush through his clearing round and therefore would have cleared the box before the time posted on the^; box, then letters that are mailed on this box after this early clearing, but before the time posted on the box, will not be delivered the next day as is targeted. The customer has with this system a guarantee for that the box can not have been inadmissible cleared before the time which is stated.

The invention is described here below as a number of preferred embodiments wherein it is referred to the accompanying drawings, in which

Fig 1 shows a flow chart for the program functions of a mail box lock,

Fig 2 shows a flow chart illustrating soft ware functions in the key for clearing the box, Fig 3 shows a function table with data base and functions for administrative handling of mail boxes and their data,

Fig 4 shows a block diagram for the mail box lock,

Fig 5 shows a block diagram for the key, and Fig 6 shows a schematical view of a mail box according to the invention with a key shown beside the box. The present invention relates to a system 1 for enabling verifiable actuation of the locks 3 of mail boxes 2 by means of a key 4, and comprises a complete solution for clearing and supervision of said clearing. The lock 3 of the respective mail box 2 is mechanical, and there is a display on the aforementioned mail box 2 or in its immediate vicinity which is arranged to show the word CLEARED or other information about clearing only during a certain time after performed clearing. With clearing time is intended the time which is presented on the notice board 50 on the mail box 2. On each one of the mail boxes 2 which are parts of said system for clearing there is a lock unit which is arranged to be programmed with a unique individual number which is unique for each respective mail box lock 3. For clearing the mail boxes 2 which are a part of the programmed clearing route for each key 4, the current appointed box is arranged to identify itself by means of the key 4 for clearing so that after approved identifying the lock 3 is arranged to be opened for clearing the box 2, preferably via a gate 6 which may be operated by the lock 3. and for subsequent activation of the clearing display (5) of the box (2) but to send code for deactivating the lock unit (3) in case of inadmissible criterion of clearing. By that, the for the box 2 intended clearing display 5 is arranged to be activated subsequently . The opening of the box 2 is thereby arranged to be performed by means of a mixture of electronic identification together with mechanical lock 3 and the clearing recording for the current route for the postman is arranged to take place during return to for example the post office, or to at other place located PC-based recording apparatus. After the performed clearing of the mail box it is arranged to be announced on for example the front 7 of the mail box that clearing has occurred, and that this information is intended to only be shown for a certain time, for example about 30 minutes after said clearing.

The lock unit comprises a lock 3 which is provided with a mounted printed board for electronic and program controlled processor. The communication between the key for clearing 4 and the lock 3 is arranged to be achieved by serial transmission of data with optical technique and that the lock electronics is arranged to be energized by contact between the key for clearing 4 and the lock 3.

The key for clearing 4 is arranged to provide the lock

3 with energy which is sufficient for ■ driving the display 5 during a certain period, for example about 30 minutes after executed clearing of the box 2. A voltage of for example +/- 6 volts is arranged to be transmitted via a mechanical terminal, that the processor is arranged to be activated and a capacitor is arranged to be charged by means of the key 4 during the lock opening stage for being supplied to the display electronics after approval of key box. This key and lock cooperation is arranged to occur as soon as communication has been established between the key 4 and the lock unit 3. Said lock unit 3 is arranged to transmit its identity number to the key 4 for clearing and that for the correct identified individual, the key

4 for clearing is arranged to activate a lock catch by means of a transmitted code.

Serinut is arranged for handling communication with the key for clearing 4 via the optical electronic serial channel and that mode choice is arranged to select the function depending on controlling data via serial channel for subsequent selection of mode for identifying or programming. The lock unit 3 is arranged to be programmed with an individual number which is arranged to be retrieved directly from the data base associated with a recording apparatus. From this, the number is arranged to be transferred over to the lock unit 3 for storing in the static RAM of the lock unit. The function reads the number from the RAM and transmits the number back to the recording apparatus for control. The recording apparatus is arranged to reply with a code verifying the correct individual number and that the communication between the recording apparatus and the lock unit 3 is performed via the optical serial channel. A solenoid is arranged to be energized for releasing a mechanical catch, so that the lock may be opened by turning the key 4. A code is thereby arranged tθ' be transmitted to an approval diode of the key for clearing 4 , so that the key 4 may be turned. The system is further so arranged, that by energizing a solenoid, a mechanical catch is released. Then the lock 3 may be opened by turning the key 4 wherein the function transmits a code to the key for clearing so that a green diode switched on in the key for clearing and which indicates that the key may be turned. Then the function controls the signal GATE-STATUS which indicates if the gate 6 opens or not and that when indicating unopened gate 6 sending a message to the key for clearing 4 which adds this to the timetable and that the message is taken care of in the recording apparatus at return e.g. to the post office.

For permitted activation of the lock catch, the gate 6 for clearing is arranged to be opened and that the display unit 5 is energized whereupon it is switched on. The display unit 5 comprises a fluorescent background projection panel. The system is arranged in such a way that clearing may take place first after that the mail box unit has been accepted by the key. The key 4 has both an electrical and a mechanical function for opening the gate 6. The key for clearing 4 has a real time clock, which is adjusted by means of the read-out apparatus of the recording apparatus. Information about clearing mail boxes 2 are collected in the key for clearing 4. The identity code of the mail box 2 plus the point of time of clearing is stored in the key for clearing 4 for read-out at return to the pick-up unit. After the clearing tour all clearings are recorded with box number and time in the recording database at the pick-up unit. After recording the memory of the key for clearing is erased and becomes passive. The key 4 must again be activated by idcode and correct authority in BOXDAB before it can be used for clearing mail boxes 4 and that if no read-out from the key 4 has occurred within for example 12 hours after activation, the memory of the key for clearing will be automatically erased and the key for clearing 4 becomes passive.

The key for clearing 4 comprises a mechanical key with integrated optical technique for communication with the lock unit 3, wherein communication is performed via serial data transmission. The key 4 also has a mechanical contact piece for power supply to the electronics of the lock unit, and that the key for clearing 4 includes a real time clock for recording clearing time at approved clearing.

The key for clearing 4 is supplied with 6 volt DC power by means of a rechargeable battery pack. The lock unit 3 receives its energy from the same battery pack via a contact piece and the key 4 is arranged to be able to, if so required, be recharged by the battery of the clearing vehicle during transport between the mail boxes. The key for clearing 4 is provided with three indicating diode lamps, that is a • yellow diode 8 for indication that communication has started between the key for clearing and the lock unit 3.

• a green diode 7 for indication that clearing may occur wherein for green diode 7, the key for clearing 4 is arranged to be actuated, e.g. turned for mechanical opening of the lock 3,

• a red diode (9) for indicating invalid clearing attempt if individual number is not correct and/or if the time for clearing is not in accordance with the timetable, and which wherein for example by blinking informs about possible low battery voltage in the key for clearing 4.

In the following is more specified what the invention comprises and how the details in it functions.

Generally The system comprises a complete solution for verifiable clearing of mail boxes. The mail box 2 is registered as individual together with clearing time. Opening of the box is performed with a mixture of electronic identification together with mechanical lock 3. After clearing is announced at the front 7 of the mail box that clearing has occurred. Information about clearing is visible for 0,5 hours after clearing.

Recording of clearing takes place at return to the post office in a PC based recording apparatus.

Terminology

BOXDAB: Database which functions for administrative handling of mail boxes and their data.

BOXSW: Software functions in the lock unit 3 of the mail box. KEYSW: Software functions in the key for clearing 4. Mail box equipment

The lock unit 3 of the mail box 2 is programmed with a unique individual number. The individual number is unique for the respective mail box lock 3. The unit handles the lock mechanism and informs customers that clearing has occurred by means of LCD display which is visible at the front 7 of the mail box.

During clearing, the box identifies itself to the key for clearing 4, permits opening of the clearing gate 6, and a performed opening of the gate 6 activates the display 5. The display 5 indicates "CLEARED" for 0,5 hours after clearing.

The functions of the lock

The lock unit 3 is based upon a mechanical lock 3 with a mounted printed board for electronic and program controlled processor. The communication between the key for clearing 4 and lock functions takes place by serial transmission of data with optical technique.

The lock electronics is energized by contact between the key for clearing 4 and the lock 3.

The key for clearing 4 provides the lock 3 with energy for driving the display 5 for 0,5 hours after clearing. See BLOCK DIAGRAM in Fig 4.

Power supply

From the key for clearing 4 is transmitted +/- 6 volt via a mechanical terminator. The processor passes from "power up mode" and becomes active. A capacitor is charged by the key 4 during the opening procedure. This energy is then used for display electronics if accepted clearing occurs. FUNCTIONS IN BOXSW

Serinut

Serinut handles communication with the key for clearing 4 via the optical electronic serial channel .

Mod choice

The function selects mode depending on controlling data via the serial channel. Mode choice is identifying or programming.

Identification

When communication has been established between the key

4 and the lock unit 6, the lock 3 transmits its individual number to the key for clearing 4. For correct identification of individual, the key for clearing 4 sends code for activation of lock catch 3.

The lock is really always passive. This makes it more difficult to try to pick the lock. The lock mechanism is activated for permissible clearing criterion and may be opened.

For non-permissible clearing criterion a code is transmitted which do not activate the lock mechanism and this will remain passive.

Programming

The lock unit 3 may be programmed with a new individual number. The lock unit is programmed from the recording apparatus. The number is retrieved directly from the database which is connected to the recording apparatus. The number is transferred to the lock unit for storing in the static RAM of the lock unit. The function reads the number from the RAM and transmits the number back to the recording apparatus for control .

The recording apparatus replies with code which verifies the correct individual number. Communication between the recording apparatus and the lock unit occurs by means of the optical serial channel. There is no limit for how many times a lock unit may be reprogrammed .

Lock catch By energizing a solenoid, a mechanical catch is released and the lock 3 may be opened by turning the key 4. The function transmits code to key for clearing 4.

Green diode is switched on in key for clearing. The diode indicates that the key may be turned.

Gate

The function controls the signal GATE STATUS which indicates if the gate 6 has opened or not. A not opened gate 6 may depend on mechanical errors in lock 3 or gate 6. For indicated unopened gate 6 is sent message to key for clearing 4 adding this to the timetable. The message is taken care of in the recording apparatus at return whereupon a new attempt to open may be performed.

Display

For permissible activation of the lock catch and that the clearing gate 6 has been opened, the display unit 5 is energized whereupon it is switched on. The display unit 5 comprises a fluorescent background projection panel. The panel is switched on when an alternating voltage is applied. The display 5 remains switched on for 0,5 hours. KEY FOR CLEARING

Clearing may occur, first after that the mail box unit has been accepted by the key 4. The key 4 has both an electrical and a mechanical function for opening the gate 6. The key for clearing 4 has a real time clock. The clock is adjusted by means of the read-out apparatus of the recording apparatus.

Information concerning clearing mail boxes 2 are collected in the key for clearing 4. The identity code of the mail box plus the point of time of clearing stored in the key for clearing 4 for read-out at return to the pick-up unit.

At return to the pick-up unit after clearing tour all clearings are registered with box number and time in the recording database . After recording the memory of the key for clearing is erased and remains passive. The key 4 must again be activated by idcode and correct authority in BOXDAB before it may be used for clearing mail boxes 2.

If no read-out from the key 4 has occurred within 12 hours after activation, the memory of the key for clearing 4 will be automatically erased and the key for clearing 4 becomes passive .

Functions in key for clearing

The key for clearing 4 comprises a mechanical key with integrated optical technique for communication with the lock unit. Communication is performed via serial data transmission.

The key 4 also has a mechanical contact piece for power supply to the electronics of the lock unit . The key for clearing includes a real time clock for recording clearing time at approved clearing.

See BLOCK DIAGRAM in Fig 5. Power supply

The key for clearing 4 is supplied with 6 volt DC power by means of a rechargeable battery pack. The lock unit 3 receives its energy from the same battery pack via a contact piece .

The key 4 is arranged to be able to, if so required, be recharged by the battery of the clearing vehicle during transport between the mail boxes 2.

FUNCTIONS KEYSW Serinut

Handles communication with lock unit 3 via the optical technical serial channel .

Mode choice

The function chooses mode depending on controlling data via the serial channel . Mode choices are identification, programming or self test.

Identification

The individual number is received from the lock unit 3. This number is compared with present individual numbers in the timetable in the key for clearing 4. For accepting the mail box, the individual number of the mail box must be present in the time table of the key for clearing and the individual clearing interval in the timetable must correspond to the real time clock of the key. Unlock

For accepted individual as well as time within the clearing interval, the key for clearing sends code to the lock unit 3 for electrical activation of the lock catch. For not permitted clearing criterion a code is sent which makes the lock unit 3 passive.

Alarm

If identification is accepted but the bottom gate 6 is not opened within the selected time, the problem is registered in the timetable. The program permits several attempts to open a troublesome gate 6.

At return to the pick-up unit, gate problems are registered also if the gate is opened after several attempts .

Registration

For approved clearing and that the gate 6 has been opened, then the current time is recorded from the key 4 real time clock 6 together with individual number for transfer to the box database at return.

Programming

The mail boxes 2 present in the time table and their respective permitted clearing interval is transmitted in the programming mode from the recording unit to the key for clearing. The real time clock of the key for clearing is updated with current date and time at programming of the clearing list.

The same optical technical incision is used for communication between the key for clearing 4 and the lock unit 3. After successful programming time for erase function is

0-set . The timetable may contain 256 individuals with their time data. There is no limit for how many times the key for clearing 4 may be reprogrammed with timetables.

Indication

The key for clearing 4 is provided with three indicating diode lamps 7-9.

Yellow diode for indication that communication has started between the key for clearing 4 and the lock unit 3. Green diode for indication that clearing may occur. For green diode, the key for clearing 4 may be turned for mechanical opening of the lock 3.

Red diode (fixed light) for indicating invalid clearing attempt. Individual number is not correct and/or if the time for clearing is not in accordance with the timetable.

Red light (blinking) low battery voltage in the key for clearing 4.

Self test Via the function in the recording apparatus a self test of the electrical functions of the key for clearing is started. Self test performs control of RAM and ROM as well as real time clock. The battery control is also performed.

Time

The key for clearing 4 contains a real time clock with 24 hours indication of time. The clock is adjusted to the correct date and time during programming of the clearing list. The function is interrupt controlled. Erase

The timetable is only active for 12 hours after charging. When the time interval has passed, all individuals are set to zero and its time in the timetable. Activation of the key 4 again occurs by means of the programming function. The function is interrupt controlled.

Battery

The voltage of the battery of the key for clearing is measured periodically. During measuring of too low battery voltage, this is indicated by the start of blinking of a red light diode.

The function is interrupt controlled.

RECORDING APPARATUS

The recording apparatus is based upon an ordinary IBM compatible PC. The PC shall be of type 486 or higher. Hard disc of min 500 Mbyte and with a primary memory of min 8 Mbyte. The recording apparatus is used both for activation of the key for clearing and for read-out of the information stored in the key for clearing 4.

All handling of the data of the mail box units is performed via the soft ware BOXDAB.

For activation of the key for clearing 4 idcode is required. This code is stored in the key for clearing 4 for read-out together with box number and current time at the return to the pick-up unit.

The read-out data may be exported in the most known data formats for possible transfer to a central database. The recording apparatus is used also when pointing out faults in the functions of the key for clearing. The real time clock may be adjusted by means of a function in the recording apparatus. The adjust function is authority protected and has in this way a limited access.

Functions in BOXDAB

Functions in BOXDAB are completely integrated under e.g. Windows 3.11. Windows 95 or in Windows NTWS .

BOXDAB is built up around a data base which handles all data connected to the respective mail box 2. The boxes 2 may be coupled together in clearing rounds. Each individual mail box 2 may be present in more than one clearing round.

The recording apparatus and BOXDAB is used when programming the key 4 with current clearing round and the clearing intervals of the respective mail boxes. The recording apparatus and BOXDAB are used also for providing the lock 3 with current individual number.

Boxadmin

The administration of clearing rounds and mail boxes 2 in the clearing rounds are performed via a completely graphical interface. The administrative data is stored in a database and is accessible directly via the graphic interface.

Mail boxes 2 may be moved between different rounds and the data of the box may be modified.

Boxlist

Outgoing from the different individuals of the clearing round and its clearing time, the key for clearing 4 is loaded with the data of the timetable. Alterations in the clearing round is handled via the function BOXADMIN. In connection with loading the timetable, the real time clock of the key for clearing is updated to the current time and date .

Boxnr

The lock unit of the mail boxes is programmed with individual number retrieved from the database. The lock unit may be reprogrammed for exchange of the lock unit .

Authority

Different levels of authority are available for handling data in the database.

Level 1 : The authority has the right to add new authorities in the database as well as the possibility to modify data in the database.

Level 2 : The authority has the right to modify all data in the database.

Level 3 : The authority has the right to load the key for clearing with the timetable from the database. The authority also gives the right to read out the key for clearing 4 to the database with the latest data of the clearing tour.

Boxreg

After performed clearing round, the stored data of the key for clearing is read out in order to update the database.

The database is updated with time for performed clearing of each separate mail box in the clearing round.

Alarm list Deviations from correct clearing generates an alarm list for analysis and measure. Key test

The function activates the self test for the key for clearing. After performed self test the function indicates its result .

The invention is however not limited to the above described and in the drawings shown embodiment of the invention but may be varied within the scope of the claims without departing from the inventive concept. For example, it is mentioned that a key is turned but the key may also be realized in the manner of a card which is inserted into an opening etc or in different ways.

Claims

C l a i m s

1. A system for verifiable actuation of the locks (3) of mail boxes by means of a key (4), characterized in that there is a display (5) on the aforementioned mail box (2) or in its immediate vicinity which is arranged to show information about clearing of the mail box (2) only during a certain time after performed clearing, that for each one of said mail boxes (2) which are parts of said system for clearing there is a lock unit (3) which is mechanical arranged to be programmed with a unique individual number which is unique for each respective mail box lock (3), that the information about the point of time of clearing of mail boxes (2) and their identity code is arranged to be stored within the key (4) for clearing, wherein for clearing the mail boxes (2) which are a part of the programmed clearing route for each key (4) , the current appointed box (2) is arranged to identify itself by means of the key (4) for clearing and after approved identifying of the individual and time within the interval for clearing, the key for clearing (4) code is transmitted to the lock unit (3) for electrical activation of the lock catch and the lock (3) is arranged to be opened for clearing the box (2) and for subsequent activation of the clearing display (5) of the box (2) but to send code for deactivating the lock unit (3) in case of inadmissible criterion of clearing.

2. A system according to claim 1, characterized in that the locking unit (3) comprises a lock (3) with a mounted printed circuit card for electronic and program controlled processor, that communication between the key (4) for clearing and lock (3) is arranged to be effected by means of serial transmission of data with optical technique and that the lock electronics (3) is arranged to be energized by contact between the key (4) for clearing and the lock (3) .

3. A system according to claim 2, characterized in that the key (4) for clearing is arranged to provide the lock (3) with energy which is sufficient for driving the display (5) during a certain period, for example about 30 minutes after executed clearing of the box (2) .

4. A system according to claim 3, characterized in that a voltage of about +/- 6 volts is arranged to be transmitted via a mechanical terminal, that the processor is arranged to be activated, and that a capacitor is arranged to be charged by means of the key (4) during the lock opening stage for being supplied to the display electronics after approval of key and box.

5. A system according to anyone of claims 1-4, characterized in that cooperation of key and lock is arranged to occur as soon as communication has been established between the key (4) and the lock unit (3) , said lock unit (3) is arranged to transmit its identity number to the key (4) for clearing and that for the correct identified individual, the key (4) for clearing is arranged to activate a lock catch by means of a transmitted code, but for inadmissible criterion for clearing, a code which do not activate the locking mechanism and which makes it remain passive is transmitted.

6. A system according to any one of claims 1-5 characterized in that serinut is arranged for handling communication with the key for clearing (4) via the optical electronic serial channel and that mode selection is arranged to select the function depending on controlling data via the serial channel for subsequent selection of mode for identifying or programming .

7. A system according to any one of claims 1-6, characterized in that the lock unit (3) is arranged to be programmed with a new individual number, the number is arranged to be retrieved directly from the data base associated with a recording apparatus, that the number is arranged to be transferred from the recording apparatus over to the lock unit (3) for storing in the static RAM of the lock unit, that the function reads the number from the RAM and transmits the number back to the recording apparatus for control, that the recording apparatus replies with a code verifying the correct individual number and that the communication between the recording apparatus and the lock unit (3) is performed via the optical serial channel.

8. A system according to any one of claims 1-7, characterized in that a solenoid is arranged to be energized for releasing a mechanical catch, so that the lock (3) may be opened by turning the key (4) , and that a code is arranged to be transmitted to an approval diode of the key for clearing (4) , so that the key (4) may be turned.

9. A system according to any one of claims 1-8, characterized in that by energizing a solenoid, a mechanical catch is released and the lock may be opened by turning the key wherein the function transmits a code to the key for clearing so that a green diode switched on in the key for clearing and which indicates that the key may be turned, that the function controls the signal GATE-STATUS which indicates if the gate opens or not and that when indicating unopened gate sending a message to the key for clearing which adds this to the timetable and that the message is taken care of in the recording apparatus at return whereupon a new attempt to open may be performed.

10. A system according to any one of claims 1-9, characterized in that for permitted activation of the lock catch, the gate (6) for clearing is arranged to be opened and that the display unit (5) is energized whereupon it is switched on which display unit (5) comprises a fluorescent background projection panel.

11. A system according to claim 1, characterized in that clearing is arranged to be permitted first after the mail box unit has been accepted by the key (4) , that the key (4) has both an electrical and a mechanical function for opening the gate (6) , that the key for clearing (4) has a real time clock, which is adjusted by means of the read-out apparatus of the recording apparatus, that information about clearing mail boxes (2) are collected in the key for clearing (4) , that the identity code of the mail box plus the point of time of clearing is stored in the key for clearing (4) for read-out at return to the pick-up unit, that after the clearing tour all clearings are recorded with box number and time in the recording database at the pick-up unit, that after recording the memory of the key for clearing is erased and becomes passive, that the key (4) again must be activated by idcode and correct authority in BOXDAB before it can be used for clearing mail boxes (2) and that if no read-out from the key (4) has occurred within for example 12 hours after activation, the memory of the key for clearing (4) will be automatically erased and the key for clearing (4) becomes passive.

12. A system according to claim 1, characterized in that the key for clearing (4) comprises a mechanical key with integrated optical technique for communication with the lock unit (3), that communication is performed via serial data transmission, that the key (4) also has a mechanical contact piece for power supply to the electronics of the lock unit, and that the key for clearing (4) includes a real time clock for recording clearing time at approved clearing.

13. A system according to claim 1, characterized in that the key for clearing (4) is supplied with 6 volt DC power by means of a rechargeable battery pack, that the lock unit (3) receives its energy from the same battery pack via a contact piece and that the key (4) is arranged to be able to, if so required, be recharged by the battery of the clearing vehicle during transport between the mail boxes (2) .

14. A system according to claim 1, characterized in that the key for clearing (4) is provided with three indicating diode lamps, that is a

ΓÇó yellow diode (8) for indication that communication has started between the key for clearing and the lock unit (3) ,

ΓÇó a green diode (7) for indication that clearing may occur wherein for green diode, the key for clearing (4) is arranged to be actuated, e.g. turned for mechanical opening of the lock (3),

ΓÇó a red diode (9) for indicating invalid clearing attempt if individual number is not correct and/or if the time for clearing is not in accordance with the timetable, wherein for ΓÇó example blinking, informing about low battery voltage in the key for clearing (4) .