Coded locking device, more especially with keyboard

In a coded locking device, unlocking of which is controlled by composing any one of two separate codes, namely a code in use known by entitled users and a responsible person or "first code x" and a secret code or "second code y", able to be derived from the first code x by a particular law known only to the responsible person, the first composition of the second code y automatically ensures unlocking of the device and, in a way sufficiently postponed for the users to become acquainted with it, the three following operations: invalidation of the first code x, adoption by the device of the second code y as new first code, sensitization of the device to a third code z derived from the preceding second code y by the above low, this third code z serving as the new second code.

The invention relates to coded locking devices, i.e. those whose unlocking 
requires the composition of a code. 
In the present description, the word "unlocking" must be interpreted in the 
widest sense of granting permission accompanied or not by an appropriate 
command, such as freeing the access to premises, to a container or to 
information, issuing tickets, and so on. 
It relates more especially to the case where the code is identifiable by a 
decimal number or the like (for example by a random succession of figures 
and letters) and may be translated by a succession of binary signals. 
It relates more especially still, but not exclusively, among these locking 
devices of the kind considered, to those which are equipped with a control 
keyboard comprising a plurality of keys identified respectively by signals 
such as figures and letters: it is known that, for unlocking such device, 
it is sufficient to compose the code by pressing successively the keys of 
the keyboard corresponding to this code. 
The safety of the locking provided by the devices considered, assumes that 
knowledge of the code remains reserved for a limited number of entitled 
users. 
When the code comes to the knowledge of unentitled users, the safety of the 
locking is no longer ensured and such safety is re-established in general 
by changing the code, the new code only being given to the entitled users. 
In known embodiments, such a change requires the visit by an approved 
specialist sent by a responsible body such as the firm who fitted the 
locking device. 
Such a requirement is complicated, long and costly. 
Moreover, it offers only a mediocre level of safety because the new code 
must be brought to the knowledge of the person making the one site change 
and each code inscribed on the device must be readily modifiable and so 
identifiable. 
To make such a visit by a specialist unnecessary, it has already been 
proposed to adapt the locking devices of the above kind so that they are 
unlockable at any time by the composition of any one of two separate codes 
namely the code in use known by the entitled users at said time or a 
"first code x" and a code secret at said time or "second code y", 
derivable from the first code x by a special law or predetermined formula, 
this law being on the one hand known by the person responsible for the 
device and being on the other hand recorded in this device so that when 
said second code y is composed for the first time, in addition to 
unlocking of the device, the following three operations are automatically 
provided: invalidation of the first code x, adoption by the device of the 
second code y as new first code and sensitization of the device to a third 
code z derived from the preceding second code y by the above law of 
derivation, this third code z serving as the new second code. 
Such an arrangement is satisfactory for locking devices in which the change 
of code may be effected immediately: this is the case when the user of the 
lock concerned is the only one, said lock being for example that of a 
hotel room; the code for opening such a lock then being changed when the 
occupant of said chamber changes in response to each newly coded key into 
said lock. 
But such an immediate change of code is not acceptable for locking devices 
likely to be actuated by a plurality of entitled users, such as is the 
case for the lock controlling the door giving access to a block of flats 
or similar comprising a plurality of occupants. 
In fact in such a case all the users of the code change to be made should 
be warned and have an "over-lap" period during which the old code remains 
still valid at the same time as the new code. 
The essential aim of the invention is to provide such a momentary "overlap" 
of the two codes. 
For this, in accordance with the invention, the three above operations are 
postponed in a predetermined way from the first time the second code y is 
composed. 
In advantageous embodiments, recourse is further had to one and/or the 
other of the following arrangements: 
the three operations initiated by the first composition of the second code 
y are postponed by a predetermined delay from this first composition, 
the three operations initiated by the first composition of the second code 
y are postponed from this first composition, until unlocking of the device 
has been carried out a predetermined number of times by composing any one 
of the codes x and y, 
means are provided, such as the illumination of an indicator light, for 
signalling to the user the "postponed code change" periods initiated by 
each first composition of the second code y. 
Apart from these main arrangements the invention comprises certain other 
arrangements which are used preferably at the same time and which will be 
more explicitly discussed hereafter.

In what follows a preferred embodiment of the invention will be described 
in a way which is of course in no wise limited to a coded locking device 
with a keyboard. In the illustrated embodiment, the locking device, which 
is denoted 10, includes a keyboard 12; comprising a pattern of keys each 
identified by a numeral or by a letter. The locking device 10 also 
includes an electronic control assembly 14, a locking control mechanism 
16, a memory 18 and a delay network 20. 
By way of example, as illustrated, the keys of keyboard 12 may be 16 in 
number, the figures numerals being the whole of those integers between 0 
and 9 and the letters A, B, C, D, E and F. 
Unlocking such a device is only possible by an entitled user, i.e. one 
knowning the code, which code is here characterized by a succession of 
figures and/or letters such for example as 724B. 
Such unlocking is provided by composing the code by successively pressing 
the corresponding keys of the keyboard 12, namely for the above example 
the keys 7, 2, 4 and B. 
To change the code for unlocking the device, this device is made responsive 
each time to two codes, namely not only the code used that time or "first 
code x", but also a code which is secret at said time or a "second code 
y", this second code being derived from the first one by a predetermined 
law or formula. 
This law is on the one hand known by the person responsible for the device, 
who may then determine the list of valid codes successively or such a list 
if several are possible. 
Said law is moreover recorded the memory 18 in the device, or more 
precisely in the electronic control assembly 14 associated with this 
device, so that this latter is capable of automatically causing successive 
code changes, each change of code being initiated automatically by 
composing the next code on the list. 
The recording in question is provided so that the composition of each 
"second code y" ensures the desired unlocking of the device and 
automatically initiates, in a deferred or postponed way, which will be 
described further on, the following three operations: 
invalidation of the corresponding "first code x", 
replacement of this first code x by the second code y as subsequent normal 
unlocking code, 
sensitization of the device to a third code z derived from the second code 
y by the above law. 
The law in question may be any of those capable of causing another number y 
or at least one of the different numbers y forming part of a well defined 
assembly to correspond to a number x, available preferably in binary form. 
In a first variant, this law is an algorithm y=(x), i.e. a succession of 
digital operations causing a single and well defined binary number y to 
correspond to each binary number x. 
In this case, the successively valid codes are x, f(x), f.sup.2 (x), . . . 
, f.sup.n (x) . . . 
In the preceding paragraph, n designates an integer, f.sup.n (x) signifies 
f[f.sup.n-1 (x)]and the symbol f(x) is equivalent to f.sup.1 (x). 
In a second variant, it is considered that each expression of the first 
code x is formed of two halves, namely a first half a and a second half b 
whose respective positions in said expression are well defined and the 
first half corresponding to the second code y is formed by the above half 
b, the second half c corresponding to this code y then automatically 
playing the role previously filled by the second half b in code x. 
Thus, in the above example, it may be considered that the two halves a and 
b of code x are respectively 72 and 4B and so form a next code y by a new 
set of four symbols, the first two of which would be 4B, the other two 
symbols being any ones and chosen by the person responsible for the 
device, but becoming definitive as soon as they are composed for the first 
time on the keyboard following the first two symbols 4 and B. 
Of course, such a solution cannot be considered in practice, for the law 
for deriving the successive codes would be immediately identifiable by the 
users knowing two such successive codes. 
This is why, in the second variant considered, the two halves a and b are 
masked. 
For this, in an advantageous approach, these two halves are formed by 
sampling the binary number corresponding to each code. 
For the code 724B, this number is: 
0111001001001011 
The half a may be formed by the digits of uneven rank of this number 
01010011 and half b by the digits of even rank 11001001. 
On this assumption, a second code y could be obtained by shifting leftwards 
by one unit all the even digits of the binary number considered and by 
choosing any values for the new digits of even rank. 
Thus, such a second code y could be, for the present example: 
1011010010000110 which number corresponds to the symbol B486. 
The sampling considered could of course be carried out in a more 
sophisticated way than the one given in the above example. 
Thus, the set of binary units, of the above binary number, corresponding to 
ranks 1, 2, 5, 6, 9, 10, 13 and 14 of said number could be adopted as half 
a. 
Sampling could also be carried out in an irregular way instead of one of 
the regular ways given as example above, the distribution of sampling 
being for example the succession of ranks 2, 3, 4, 6, 9, 10, 12 and 16. 
It should be noted that with this second variant, each new code y is not 
completely determined beforehand depending on the preceding code x. 
In fact, the "second half" c of said new code y - which comprises b as 
first half - is left to the choise of the person responsible for the 
locking device and only becomes definitive after the first effective 
composition of this new code y. 
In another variant, based on the same principle, the law for deriving each 
code y from a code x expressed in binary number form consists in 
suppressing the first binary digit of this number, in shifting all its 
other units leftwards and replacing the last binary digit by a new one 
which may again be chosen by the responsible person. 
For the example chosen above, that would mean adopting for code y one of 
the following two: 
0110100100001100 or 
0110100100001101 which correspond respectively to the symbols 690C and 
690D. 
As mentioned above, invalidation of the code in use is not effected 
immediately after the first composition of a new code, but postponed so 
that the users of the device are not taken unawares : the two codes 
considered thus remain valid simultaneously for a period during which the 
users are informed. 
For this, delay means 20 are provided in the locking device for 
automatically postponing by a delay R, from the first composition of a new 
code, the invalidation of the code in use as well as the other two 
operations which are associated therewith. 
Thus, if the locking device 10 is used to equip a door giving access to a 
block of flats, the delay R may be a day so that all the inhabitants of 
the block of flats may be warned of the change of code to be made. 
In a variant, the delay R may be defined not by a period of time, but by a 
predetermined number N of compositions of the code in use and/or of the 
new code : thus, for the above mentioned application to the unlocking of 
the door of a block of flats, if the means number N of operations for 
opening this door is 100 per day, initiation of the three above operations 
may be postponed until such opening operations have been effected 100 
times, using any one of the two codes, from the first composition of the 
new code. 
In a particularly advantageous embodiment, signalling means, such for 
example as the lighting of an indicator light 22, are provided for 
informing the user that the locking device 10 is in its "postponed code 
change" period, which period is initiated by the first composition of a 
new code, so as to inform said user of the imminent change of the code or 
incite him to make enquiries if he does not know the new code. 
In preferred constructions of the above locking devices, the successive 
codes are recorded in the electronic memory 18, for example a 
semiconductor memory, supplied by a safeguard battery 14 or adapted so 
that successive code recordings and deletions may be effected therein by 
electric control and so that the recorded codes are kept therein even in 
the absence of any electric power supply. 
Following which, and whatever the embodiment adopted a coded locking device 
is finally obtained which lends itself in an extremely simple and flexible 
way to a code change. 
In fact, for making such a code change, it is sufficient for the person 
responsible for the locking device to inform one of the entitled users of 
the new code to be adopted and for this user to compose this new code so 
that the device automatically adopts this latter code after a period of 
time for the users to become acquainted with it. 
As is evident, and as it follows moreover already from what has gone 
before, the invention is in no wise limited to those modes of application 
and embodiments which have been more especially considered; it embraces, 
on the contrary, all variants thereof, particularly those in which the 
number of codes (x.sub.1, x.sub.2. . . ) normally in use at a given time 
or during a given period for actuating the locking device is greater than 
one, as is the case for locks actuable by two different day and night 
codes, or else for locks actuatable by codes graded for actuating 
respectively different numbers of locks and brought to the knowledge of 
users complying with different criteria of entitlement, each of these 
codes x.sub.1, x.sub.2 being able to be "changed" automatically on the 
spot by simply composing a "next code" (y.sub.1, y.sub.2) after a 
predetermined delay (R.sub.1, R.sub.2) following such composition of the 
number, the different delays considered being possibly different from one 
code to another.