DE3323285A1 - Method for monitoring keyboards in digital telecommunication terminals - Google Patents

Abstract

The invention relates to a method for monitoring keyboards in digital line-fed terminals for key pressure. Keys arranged in columns and rows are monitored by applying a test potential row by row and testing for existing potential column by column. The object of the invention consists in carrying out the monitoring in the idle state with a minimum of energy. This object is achieved by the device sending out the test potential being switched inactive in the idle state, all rows being connected to 0-potential via a switching section controllable by a flip flop and all columns additionally being connected to the inputs of a common NAND gate for setting up the potential test and, on key actuation, the 0-potential of the corresponding row passing via the NAND gate to the flip flop, disconnects the 0-potential from all rows and switches on the device sending out the test potential. Thus, the active energy-consuming keyboard monitoring arrangement is only switched on during the keyboard operating time.

Description

Method for monitoring keyboards in digital remote

reporting devices.

The invention relates to a method for monitoring keyboards in digital telecommunication terminals at the push of a button, with the individual Keys are arranged in columns and rows, with a decoder for row by row Creation of a test potential and a register for evaluating it column by column Test potential and thus for marking a pressed key are provided.

In the case of digital terminals, in particular telecommunication terminals, the Particular importance should be attached to power consumption, especially when the device is idle. Especially in the case of devices fed via the subscriber line, the energy consumption must be as low as possible. In relation to the keyboards of such devices, the Request, for example, for the performance feature "Dial when the handset is on-hook" necessary to constantly query all keys at any time, even in the idle state, whether a key is pressed. Thus, a "key query module" is permanent actively in operation.

To reduce the energy requirement, it is now the object of the invention, to find a method with the help of which it is possible that the "key query module" and so that the keyboard is only scanned at the point in time at which the keyboard is activated is actually used and that in the idle state the keyboard this is monitored in another energy-saving way at the touch of a button.

This is achieved by providing one transistor per row which connects the respective row with 0 potential in the low-resistance state, that each column is connected to one input of a NAND gate, im Idle state via the NAND gate a flip-flop is controlled so that it is over their first output, the transistors, and the decoder on the input side controls high resistance and wherein when leaving the idle state by pressing a Press the button and thus change the potential of a NAND gate input via the flip-flop the NAND gate output is controlled in such a way that the transistors via the first output controls the input of the decoder with high resistance and thus an active one Keyboard state is reached.

This has the advantage that during the compared to the active State very long idle state of the keyboard this only through applied static Potentials is monitored and that the active one immediately when a key is pressed The keys are scanned to characterize the state of the keyboard.

The method according to the invention is explained with the aid of a figure.

The figure essentially shows the keyboard with lines Z1 to Zn, the columns S1 to Sm and the intersections P11 to Pnm, a decoder D. Register R, a NAND gate N, an OR gate OR, a flip-flop K, the transistors T1 to Tn and a further transistor ST, referred to as a switching transistor.

To explain the underlying the procedure circuit should be assumed that the keyboard is in idle mode. It is in this state the flip-flop K is set in such a way (e.g. via the reset input R - line d) that its Output Q has a potential h. So that the decoder D via the line f and the control input c controlled high resistance and the transistors T1 to Tn are low resistance. O potential is now applied to all rows Z1 to Zn via the transistors T1 to Tn at. On the part of the register R, there is an h potential at all columns S1 to Sm at. This h-potential is thus present at the same time via the lines al to am all inputs of the NAND gate N. At the output of the NAND gate N and thus at the input S of the flip-flop K is an L potential, which is the current switching state corresponds to the flip-flop K.

At the output Q of the flip-flop K there is an L potential which is above the line g is at the same time at an input of the OR gate OR. There on the other Input of the OR gate via line e also has an L potential an L potential at the control input of the switching transistor ST. The switching transistor is therefore blocked and thus separates the voltage U from a scanning device Sc. This scanning device is thus inactive and received via the lines bl to bn the decoder D does not have any scanning potentials.

This means that the keyboard is idle and there is nothing worth mentioning Energy consumed.

If a key is now pressed, e.g. at node P2m of the keyboard, then the h-potential of the column Sm is immediately derived via the transistor T2 and an O potential (or L potential). This results in the flip-flop at input S. No h-potential, at output Q also an h-potential and at output Q an L-potential.

This means that now all transistors T1 to Tn are high-resistance (no more 0 potential on the lines) that the decoder D has a low resistance via its input c is controlled that at the output of the OR gate there is an h potential, whereby the Switching transistor ST becomes low-resistance and puts the scanning device Sc into operation, which now over the lines b1 to bn one line after the other with a scanning potential scanned so that the register R can recognize via the columns S1 to Sm which Button was pressed.

The keyboard changes from this active state to the end of the scanning process returned to their idle state, for example by a pulse on the reset input R of the flip-flop K.

On the other hand, the keyboard should be switched from the idle state to the active one State without pressing a key, then the line e is sent to the OR gate given an h potential, as a result of which the switching transistor ST becomes low-resistance, the scanning device puts into operation and at the same time the flip-flop via a set input E into the brings the correct switch position.

4 claims 1 figure

Claims (4)

I'a t ttl t [tr! T $ tt'ii (ri method for monitoring keyboards in digital telecommunication terminals at the push of a button, with the individual Keys are arranged in columns and rows, with a decoder for row by row Creation of a test potential and a register for evaluating it column by column Test potential and thus a pressed key for marking are provided, d a d u r c h g e -k e n n z e i c h n e t that per line (Z1-Zn) one transistor (T1-Tn) is provided, which in the low-resistance state, the respective line (Z1-Zn) with 0 potential connects that each column (S1-Sm) each with an input (via al-an) of a NAND gate (N) is connected, with a flip-flop via the NAND gate (N) in the idle state (K) is controlled so that the transistors (T1-Tn) via their first output (Q) low-resistance and the decoder (D) on the input side controls high-resistance and with leaving the idle state by pressing a key and thus changing the potential of a NAND gate input controls the trigger (K) via the NAND gate output becomes that it has high resistance and via the first output (Q) the transistors (T1-Tn) the input of the decoder (D) controls low resistance and thus an active state of the Keyboard is reached. 2. The method according to claim 1, d a d u r c h g e -k e n n z e i c h n e t that after the localization of an actuated key the active state the keyboard by activating the reset input (R) of the flip-flop (K) and thus Reversing the flip-flop (K) is ended. 3. The method according to claim 1, d a d u r c h g e -k e n nz e i c h n e t that the flip-flop (K) has an OR gate via its second output (Q) (OR) controls so that this one a scanning circuit for the decoder (D) at- and switching transistor (ST) in the idle state high resistance and in the active State switches to low resistance. 4. The method according to claim 1 and claim 3, d a d u r c h g e k e n n n z e i c h n e t that via a second input of the OR gate (OR) by applying an h-potential the keyboard without pressing a key in the active state is brought.