Patent GB-1492376-A (GB)
Title: Hand held interactive terminal
IPC: H03M11/14
Filed: 1974-11-18
Abstract: 1492376 Hand-held computer terminal; keyboards and displays TERMIFLEX CORP 18 Nov 1974 [21 Nov 1973 6 May 1974] 49791/74 Headings G4A and G4H A terminal 20, for communicating with external data processing means, includes an alphanumeric display 22 for presenting data received and transmitted, a data memory for storage of the data received and transmitted, and a keyboard 24, operable by a user's first hand, including a plurality of keys each being capable of transmitting a plurality of different data levels, a particular data level being selected by shift level control keys 26-28 mounted on a side face of the terminal housing so as to be operable by the fingers of the user's second hand. As described, four data levels are selected by three shift level control keys, but a smaller or a larger number of the (two-position) shift level control keys may be used for selecting the four data levels. Indicator lights may be provided to indicate the actuation of a particular shift level control key. A three-position scroll switch 30 may be provided for displaying data as received, for sequentially displaying data held in the data memory, and for holding data on the display. The sequential displaying may be achieved by scrolling the lines of the display upwards or downwards. Horizontal scrolling may also be employed (no details). Actuation of a key of the keyboard 24 generates a 5-bit signal which accesses a corresponding 6-bit word representing the character or contact signal associated with that key from a read-only memory. The 5-bit word is provided with start and stop bits and the resultant 8-bit word is serially transmitted to the external data processing means. The transmission may be to a teletypewriter via a telephone link or by means of a battery-powered radio frequency transmitter which may be incorporated within the terminal housing. In the full-duplex mode of transmission, the received 8-bit word is transmitted back to the terminal for display, whereas in the half-duplex mode, the display occurs at the same time as the 8-bit word is being transmitted to the external data processing means. In either case, the 6-bit word (the 8-bit word received by the terminal having been stripped of its start and stop bits) is stored in a character memory comprising six 1000-bit recirculating shift registers coupled in parallel, each receiving a respective bit of the 6-bit word. The word storage is interlaced. In a modification, the character memory comprises six 100-bit recirculating shift registers. The 6-bit word, read from the character memory, is fed to an ASCII font generator which generates 5-bit words which in turn determine the form of the displayed character. In the preferred embodiments the display 22 comprises two lines each of ten character positions, each character position comprising a 7 x 5 dot LED matrix. The terminal is able to transmit and receive data at any of four different manually-selectable speeds (BAUD rates), the 8-bit serial data words being optionally provided with two parity bits, either for even or odd parity, and an additional stop bit. Actuation of a key 41 in the appropriate data level causes an ASCII break character to be generated, the terminal then being disconnected from the external data processing means and operating in a LOCAL mode. Actuation of a key 36 in the appropriate data levels causes either the upper case alphanumeric characters of the keyboard 24 to be substituted by the lower case, or vice versa depending upon which case is currently in use, or causes control signals to be generated instead of the alphanumeric characters. A cursor may be displayed indicating the position, the type and the data level of the next character to be generated, and the cursor may be arranged to blink to distinguish it from other displayed characters. If the cursor is not being displayed, the display is arranged to blink when data is being received by the terminal while other data is being displayed. The display automatically dims if no data is received or generated on the display for approximately five minutes. A JUSTIFY feature is also provided which prevents the displaying on two lines of a word of 10 characters or less. If any key of the keyboard 24 is held depressed for approximately one second, automatic repetitive transmission of the character associated with that key is initiated. A similar automatic repetitive scrolling of the display 22 is initiated if the scroll switch 30 is held in the scroll advance position for approximately one second. Data is not transmitted if two or more keys of the keyboard 24 are actuated simultaneously, a bell then sounding to indicate an error condition. The bell also sounds for other improper actuations of the keys of the keyboard 24 and when an ASCII BELL code is received from the external data processing means. Latching keys (33-35), Fig. 1 (not shown), may be provided on the front face of the terminal housing, the keys (33-35) paralleling the keys 26-28 so that the terminal may be operated with one hand as a normal "desk" terminal. The arrangement and details of the logic circuitry of the terminal are illustrated in Figs. 2-8 and 12-25 (not shown).