Abstract:
The present invention is an improved data terminal for use in communication and testing of telephone lines which data terminal is operated by a 16-bit microprocessor operating under control of MS-DOS 5.0 program. The data terminal with operating computer and large plurality of telephone test functions is fully contained in a hermetically sealed, lightweight housing to enable easy field handling through data send and receive operations as well as the multiple of telephone line test operations. Power saving aspects of the invention include automatically adjusted LCD backlight control and LCD adjustment caused by large or abrupt temperature changes in the field. The system uses a large microprocessor with EPROM and random access memory with field programmable gating arrays offering virtually thousands of different gate logic decisions.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to U.S. patent application Ser. No. 07/514,318 which was filed on Apr. 23, 1990, now abandoned and entitled &#34;DATA TERMINAL FOR COMMUNICATING OVER A TELEPHONE CIRCUIT&#34;. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to data terminals for communicating over telephone circuits, and more particularly, but not by way of limitation, to a terminal for communicating with a telephone operations and administrative system, one specific type of which is referred to as a craft technician&#39;s portable field terminal through which telephone maintenance dispatches and reports are made. 
     2. Description of the Prior Art 
     In the telephone industry, individuals, referred to as craft technicians, are utilized in the field traveling from site to site where telephone instruments or telephone facility problems are found. Typically, maintenance requests are collected at a central location and then dispatched to different individuals for attention. Once a problem has been attended to, the craft technician must report results back to the central location. 
     Computerization of such maintenance systems has enabled the craft technicians to receive dispatches and submit reports without having to travel to and from or to verbally communicate with the central maintenance location. The craft technician can now communicate with the central location through a hand-held portable field terminal such as is disclosed in U.S. Pat. No. 4,837,811 in the name of Butler et al. This computerized maintenance system along with the advent of the technician&#39;s field terminal has significantly improved the efficiency of telephone systems. 
     Although terminals such as the type disclosed in U.S. Pat. No. 4,837,811 have proved advantageous, there are additional needs to be met to enhance further the utility of such terminals. One such need is to enable such terminals to receive programs, such as applications programs which the technician may wish to call up in order to perform a specific task (e.g., creating and filling out a time sheet), which are downloaded over conventional telephone circuits. In order to save time, the technician no longer need take the terminal into the central office in order to be reprogrammed over a high speed data link, but he can download additional programs directly to the terminal at its remote location via the existing telephone circuit. 
     SUMMARY OF THE INVENTION 
     The present invention provides a novel and improved data terminal for communicating over a telephone circuit. The data terminal utilizes a single microprocessor and a minimum one meg storage while operating on MS DOS (Version 5) to enable a plurality of circuit functions including multi-mode communications, selected telephone test functions, LCD brightness control functions, temperature compensation features and continuous power management functions. The data terminal includes an LCD display (40×25) and all of the standard personal computer function and control keys including a QWERTY alphanumeric keypad and a standard telephone keypad. In addition, the data terminal is packaged in a lightweight, hermetically sealed and weatherproof encasement thereby to provide the craft technician with greatest repair and communication capability under all field conditions. 
     It is an object of the present invention to provide a craftsman&#39;s data terminal that is programmable based upon the DOS platform. 
     It is also an object of the present invention to provide a data terminal that can be readily upgraded in the field by switching modular modems and which can add additional random access memory by modular exchange. 
     It is still further an object of the present invention to provide a data terminal having increased area of liquid crystal display which has automatic contrast and backlighting control. 
     It is yet further an object to provide a data terminal having multiple modes of communication including DTMF signalling as well as amplified loud speaker output that provides a high-impedance monitor for subscriber lines. 
     Finally, it is an object of the present invention to provide a data terminal housed in a compact, lightweight package that is totally waterproof and capable of telephone subscriber line voltage measurements with up to 15 mv accuracy. 
     Other objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawings which illustrate the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the data terminal as constructed in accordance with the present invention; 
     FIG. 2A is an exploded view in section of top and lower panels of the data terminal container; 
     FIG. 2B is a plan view of the interior side of the top panel of the data terminal; 
     FIG. 3 is a schematic drawing of the top half of the microprocessor circuitry of the present invention; 
     FIG. 4 is a schematic drawing of the bottom half of the microprocessor circuitry; 
     FIG. 5 is a schematic diagram of the memory section of the present invention; 
     FIG. 6 is a schematic drawing of the keyboard and LCD control circuitry of the data terminal; 
     FIG. 7 illustrates connections for specific circuits in relation to a three-ganged field programmable gate array (FPGA) circuit; 
     FIG. 8 is a schematic illustration of a universal asynchronous receiver-transmitter (UART) stage in the present invention; 
     FIG. 9 is a schematic drawing of the caller number delivery (CND) circuitry of the data terminal; 
     FIG. 10 is a schematic drawing of the caller number delivery modem circuit of the present invention; 
     FIG. 11 is a schematic illustration of the display backlighting circuitry of the present invention; 
     FIG. 12 is a schematic drawing of the dial tone multi-frequency (DTMF) receiver-transmitter of the data terminal; 
     FIG. 13 is a schematic drawing of liquid crystal display contrast circuitry and LED control leads in the present invention; 
     FIG. 14 is a schematic diagram of a voice switched speaker phone circuit as utilized in the present invention; 
     FIG. 15 is a schematic diagram of a high impedance monitor circuit constructed in accordance with the present invention; 
     FIG. 16 shows schematically a portion of the speaker phone circuits utilized in the present invention; 
     FIG. 17 is a schematic diagram of analog to digital converter used in the light sense and temperature sense circuitry of the present invention; 
     FIG. 18 is a schematic diagram of a digital to analog converter of the present invention as utilized with the speaker and speaker phone circuits; 
     FIG. 19 is a schematic diagram of a digital to analog converter as used with the display light control and caller number delivery modem in the present invention; and 
     FIG. 20 is a schematic diagram of power supply and attendant energy management unit as utilized in the present data terminal. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the data terminal 10 consists of a housing or container 12 having sidewalls 14 and top panel 16 in water-tight assembly, as will be further described. The data terminal has a 320×200 dot TN LCD panel 18 of the transflective type with automatic CFL backlighting and eighty-one embossed tactile keys with embedded LED indicators. The keys consist of function keys 20, a telephone keypad 22, a standard QWERTY keyboard 24, with the remainder being the various control keys of standard PC-compatible type including special keys, panning and scroll keys, etc. 
     A hands free speaker 26 is placed in the sub panel position designated by dash lines and a microphone function is provided by an embedded electret 28. An optical light sensor 30 provides an ambient light detector for use in controlling contrast of LCD screen 18, and a plurality (eight) of LED function indicators are provided at 32. A battery charge jack 33 is provided and a twenty-five pin LPT1 parallel port receptacle 34 is available adjacent thereto. An RS-232 receptacle 35 appears on the right hand side while line 1 and line 2 (data/voice and voice) RJ-11 telephone receptacles 36 and 37 are readily accessible. 
     FIG. 2A shows in exploded form the manner in which the top panel 16 and integrally formed side walls 14 are engageable with a bottom panel 38 to form a hermetically sealed container 12. The side walls 14 of the upper half structure are actually rectangular or nearly square in configuration and the lower edge 39 of side walls 14 extends a nearly square sealing tongue 40 therearound. The bottom panel 38 extends unitarily an upwardly facing lip 41 of nearly square configuration which includes a nearly square groove 42 for mating reception of the downward facing insert tongue 40. In actual assembly, a length of elastomeric gasket material is disposed around the groove 42 with subsequent force-fit of tongue 40 downward therein and suitable bonding around the total, nearly square extremity. A plurality of securing posts 43 and 44 are located around the inner side of top panel 16 and lower panel 38 for water tight reception of selected fasteners. 
     FIG. 2B is a view of top panel 16 showing the inner structure. The top panel 16 includes a rectangular hole 45 through which the LCD panel 18 is viewably mounted, and it includes other strategically located securing posts 46 and 47 disposed for mating engagement with opposite securing posts within the lower panel 38. A circular rib structure 48 provides a mounting space for the device speaker 26. 
     FIGS. 3 and 4 relate to the microprocessor 50 and attending circuitry. The microprocessor 50 is a Chips and Technology Type F8680 and it functions in conjunction with an EPROM 52, an Intel Type 27C020, a reprogrammable 256 kb Flash EPROM. Referring to FIG. 4, there is also provided a coactive random access memory 54 which is Motorola Type 62250. 
     The address ports ADR00-ADR25 are each connected into an address bus 58 while ports 00-17 are also connected into the address ports of EPROM 52. The output data ports D0-D7 from EPROM 52 are connected onto the bi-directional data bus 60. The data ports RD00-RD15 of microprocessor 50 are connected onto a bi-directional data bus 62. Interrupt request leads IRQ2-IRQ7 are connected via lead group 64 into the respective ports of microprocessor 50 and the data request ports receive input of the DRQ1-3 leads 66. In like manner, inputs are received for IOCHRDY channel ready and IOCHCK channel check on respective leads 68 and 70. Power up PWRUP on lead 72 is received in from the power on indication at terminal 74, and system reset is provided on lead 76. U-clock is received on lead 74 from the 1.6432 megahertz oscillator 76 and RTC clock is received on lead 78 from a 32.76 kilohertz oscillator 80. A T clock input on lead 82 is derived from a 14.318 megahertz oscillator 84. 
     Dynamic memory access acknowledgment signals DACK 1-3 are output on lead group 86 and terminal count output TC is presented on lead 88. Chip select ROMC50 and memory write SMEMW control are provided on leads 90 and 92 to the EPROM 52. Lead group 94 provides input to the microprocessor 50 of address enable AEN, address latch enable ALE, read IOR and write IOW on lead group 94. Memory read JMEMR and memory write SMEMW outputs are provided on leads 96 and 98 while refresh RFSH output is on lead 100, system clock on lead 102 and speaker control on lead 104. Oscillator power on lead 106 returns to receive data circuitry as will be further described. 
     Referring now to FIG. 4, the lower half of microprocessor 50, the lead group 108 provides power supply condition inputs to ports PS1 through PS4 and lead group 110 provides memory card data to the memory card ports MCBAT 1 through MCRDY. Various chip select CS functions are attended by lead group 112 and selected read and write chip commands are provided on leads 114. Enablement of memory cards 1 and 2 is controlled by lead group 116. Lead group 118 controlling transmit data TXD, ready to send RTS and data terminal ready DRT is input to a voltage converter 120, a Maxim Type 239. The voltage control output is then presented on lead group 122. Input at lead group 124 consisting of receive data RXD, clear to send DTS, data set ready DSR, data carrier detect DCD and ring indicator RI is applied to ports RX0-RX4 of the voltage converter 120 and regulated outputs D00-D04 are conducted on lead group 126 for return to the respective ports R1-RXD of microprocessor 50. 
     Keyboard data and keyboard clock signals are connected on leads 128 from the keyboard. Ports GRA0-GRA14 provide graphics address to ports A0-A14 of RAM 54 and input-output ports 0-7 provide interconnection on lead group 130 back to the graphics data ports GRD0-GRD7 at microprocessor 50. The chip select, read enable and write enable of RAM 54 are attended by lead group 132. Intelligence depiction of graphics is controlled by the output ports for dot, i.e., lead group 134 which are applied to the liquid crystal display terminals. 
     FIG. 5 represents a memory circuit that functions in conjunction with the microprocessor 50 and which maintains storage of the MS DOS 5.0 program. The storage is effected by a pair of DRAMS, Hitachi Type 4C8512 Kx 8 bit DRAM circuits, which DRAMS 140 and 142 operate in parallel. The respective address lines 01-11 are each current limited and placed onto a memory address bus as lines MA01-MA11 present on memory address bus 144. Address input is then derived from memory address bus 144 for input to respective A0-A9 inputs of each of DRAMS 140 and 142. 
     The DRAMS 140 and 142 operate in tandem as chip select CS 20 signal on line 146 is applied to respective RAS ports and chip select CS 11 and chip select CS 10 are applied via respective leads 148 and 150 to the CAS ports of DRAMS 140 and 142. Read OE and write WE inputs on leads 152, 154, 156 and 158 are also applied in control of respective DRAMS 140 and 142. Additional chip select signals on leads 160 and 162, CS22 and CS21, are available as output for microprocessor 50. 
     Each of the DRAMs 140 and 142 is controlled to output D0-D7 8-bit data onto a data bus 164. Each of the DRAMS 140 and 142 has the capacity of 512 kilobytes so that the total storage capacity is normally 1024 kilobytes. This dynamic RAM storage is used to contain the MS DOS program information and it can be readily expanded up to 4 Mb by modular insertion of storage components if such additional memory is required. 
     Referring to FIG. 6, there is shown circuitry for keyboard scanning data compilation and logic circuitry for the liquid crystal display. While the keyboard circuitry is not shown specifically in the interest of eliminating clutter, the data terminal 10 utilizes a standard type of keyboard matrix array that can be readily scanned by examining the rows and column circuit condition for each matrix interconnection. Thus, the lead groups 168 and 170 each provide 4 lead input to the A0-A3 ports of respective tri-state buffers 172 and 174. The tri-state buffers 172 and 174 are Motorola Type 74HC244 integrated circuits and they receive enable voltage via lead 176 from the I07 port of a programmable array logic circuit 178, Atmel Type PAL 16VS. A pair of Y0-Y3 outputs from respective tri-state buffers 172 and 174 is then output onto data bus 60 as binary signals RD00-RD07. 
     Address lines ADR 00-ADR15 are applied on an address bus 180 through respective diodes to emerge as matrix row signals KR00-KR15 on bus 182. The programmable array logic 178 is connected with 20 grounded read enable (OE) port, and ADR 24 from address bus 58 is connected to port 18. The SMEMR output on lead 96 (FIG. 3) connects to port 17 while refresh output on lead 100 connects to port 14. The WEI and WEO signals from microprocessor 50 and lead group 114 are connected to respective ports 16 and 15, and liquid crystal display outputs FP, LP and CP from lead group 134 (FIG. 4) are applied to respective ports 13, 12 and 11 of PAL 178. The ROM chip select voltages are applied to I/O ports 1 and 2 while address lead ADR 23 from bus 58 is applied to the I/O port 3. Refresh voltage is present on lead 184 (I/O 5) and the ROM chip select voltages for ROMs 0 and 1 are present on respective leads 186 and 188. 
     Referring now to FIG. 7, there is a tandem interconnection of field programmable gate arrays of Type XC 3020 which are available from Xilinx Corp. The field programmable gate arrays are commonly referred to as FPGA circuits and three identical FPGA chip circuits 190A, 190B and 190C are utilized in the overall circuit. The FPGA has the capability of being pre-programmed so that selected gating arrangements are effected between signals at selected I/O ports. The program allows wide variation in the number and association of outputs versus inputs as utilized on a respective FPGA. The program for present design of FPGAs 190A-C is a fifty page document and is submitted herewith as Exhibit 1. 
     The three FPGA circuits 190A, 190B and 190C are synchronized as a unit by interconnection of their respective pins 60 clock inputs as tied together by control lead 192. Each of the FPGAs 190A, 190B and 190C is energized by application of 5 volts power to pin 10, the power PWRON connection which includes the memory 0 and 1 receive trigger and receive data inputs in parallel. Generally, each of the FPGA integrated circuits 190A, 190B and 190C deals with a separate plurality of the different circuit functions that occur in the operation of the data terminal 10. 
     Referring now to FIG. 8, a chip 194 is a silicon systems Type 73M1450 universal asynchronous receiver/transmitter which is commonly referred to as a UART. A UART chip functions to link the device 10 circuitry up to a standard type of modem which is connected to an external telephone line. A 1.8432 megahertz oscillator 196 is connected between the XIN and XOUT ports and the remaining ports on the left hand side connect from other circuits. Thus, noting also FIG. 7, the UART RXD input as applied to the SIN port is connected from the I/O-HDC port (pin 28 of FPGA 190C). The COM2-TXD port is output to the communications 2 transmission channel. The UART DCD signal input to UART 194 comes from terminal 198 (pin 27) of FPGA 190C, and the UART DSR data set ready signal is applied to terminal 200 (pin 34) of FPGA 190C. Connection of DTR data terminal ready and RTS ready to send are outputs and CTS clear to send and RI ring indicator receive inputs. 
     Referring again to FIG. 8, binary data signals are received in at ports D0-D7 from the data bus 60, and terminals A0, A1 and A2 receive address signals A00-A02 from the address bus 58. Also, IORD read and IOWR write signals are input to their respective ports as derived from lead group 94 (see FIG. 3) and the communications port 2 chip select is available from FPGA 190B at pin 68, the I/O A5 port. The interrupt signal from communications port 1 is then applied as interrupt for the UART 194. 
     FIG. 9 illustrates the telephone line input circuitry for both lines 1 and 2. The line 1 inputs consist of tip and ring terminals 202 and 204 with an amplifier 206 interconnected to detect an incoming signal on line 1. Upon detection of a signal, a signal is produced at terminal 208 line 1-TR, and this signal is applied to an analog to digital converter in FIG. 17, as will be further described. In the event of a signal input L1 HOLD at terminal 210, the solid state switch 212 will be energized to latch the hold circuit closed. Ring voltage on lead 204 also will close the switch circuit 214 to place caller identification signal on the primary of a transformer 216 with the line 1 caller number delivery signal present on output terminal 218. 
     The line 2 tip and ring leads 220 and 222 span a similar amplifier 224 which produces a line 2 TR signal at terminal 226. The signal at terminal 226 is also applied to an analog to digital converter as will be discussed relative to FIG. 17. A solid state switch 228 is connected as a ring indicator to provide line 2 RI indication on output terminal 230. Solid state switch 232 then functions as a hold circuit to enable the line 2 HOLD output at terminal 234. 
     Referring now to FIG. 10, a caller number delivery (CND) circuit receives input of the line 1-CND signal as output from terminal 218 (FIG. 9) for connection to terminal 236 and the RXA input of a CND modem 238, a Motorola Type TCM3105 which functions to retrieve the caller ID number off of the incoming line. An oscillator 240 operating at 4.4336 megahertz is input across the oscillator 2 and oscillator 1 inputs of modem 238. The CND V1 and CND V2 voltages are derived in FIG. 19 (to be described) and applied to the RXB and CDL inputs of modem 238, and the outputs are generated in digital signal form as the CND RXD and CND DCD/DSR control signals which indicate data carrier detect and data set ready, for input to FPGA 190C at I/O48 and I/O45 (FIG. 7). 
     FIG. 11 illustrates one form of voltage regulator that is utilized in the LCD backlight circuitry. A backlight enable signal BKLT EN is applied to input terminal 244 and is derived from I/O 54 of FPGA 190A. This signal is applied through transistor switch 246, a Type S19953 for conduction through parallel diode 248 to an output lead 250 which conveys the BACKLIGHT control voltage output. A solid state voltage regulator 252, a Type LM317, is connected in parallel to control the level of voltage at output terminal 250. Inputs from FPGA 190B, viz. A00 at I/O A2, BKLT WR at I/O CSI (actually a chip select) and I/O WR at I/O 39, are applied in control of a digital resistor 254, a Dallas Semi-Conductor Type DS1666SN, to provide adjustment via lead 256 of the output 250 of voltage regulator 252. The transflective LCD screen is clear and viewable with sufficient ambient light but may need additional backlighting at low ambient light levels. 
     FIG. 12 shows a dual tone multi-frequency (DTMF) receiver-transmitter integrated circuit chip 258, a Silicon Systems Type 75T2091. Eight bit binary digital input is applied to DTMF D0 through DTMF D7 terminals from respective terminals located on the FPGA 190C. The LATCH PORT of the DTMF receiver-transmitter 258 is connected to DTMF WR on FPGA 190B, as is DTMF CLK in connection to the ATB port (pin 15). The DTMF output is present on port terminal 260. 
     Referring now to FIG. 13, a CTRLV CONTRAST signal 344 (from FIG. 19) is input to the positive terminal of an amplifier 262 which generates an output on lead 264 that automatically adjusts the contrast condition of the liquid crystal display when temperature change may have caused detrimental contrast change. The software determines the connecting contrast voltage by accessing a look-up table based upon the current temperature system voltages. Also indicated in FIG. 13 is the manner in which a series of outputs 266 as derived from selected ports on FPGA 190A are conducted through respective current limiting resistors 268 to become the energizing voltages for the plurality of front panel LED light indicators. 
     FIG. 14 represents a speaker phone circuit as utilized in the present device wherein a Motorola Type MC 341180 voice switched speaker phone circuit functions. The SP C1 and SP C2 inputs are derived from FIG. 16 as will be described. The DTMF OUT on lead 260 (FIG. 12) is applied as input to the HTI port of IC device 270. Also, a D2A SP analog signal output as derived from speaker phones is present on lead input 272 and also connected to the HTI port of chip 270. Yet additional inputs SP Cl and SP C2 are obtained from a coupling transformer in FIG. 16, as will be further described, for input via leads 274 and 276. Speaker phone signals SP EN and SP MUTE are applied at inputs 278. Microphone input on lead 280 is applied to the MCI port of chip 270 and outputs generated are conducted on speaker output lead 282 and speaker phone output 284. The speaker phone mute and enable signal inputs at 278 are derived from the FPGA 190A (FIG. 7) and the signal on lead 272 is derived from a digital to analog converter in FIG. 18 as will be described. The speaker phone C1 input at lead 286 to port FO of speaker phone chip 270 allows sound actuated switching of the speaker phone circuit. 
     FIG. 15 is a high impedance monitor circuit controlling system audio. An integrated circuit 288 is a digital resistor, a Dallas Semi-Conductor Type DS1666SN, which functions to control volume of the speaker. Control inputs of A00, volume WR, and IO WR are connected to respective I/O ports A3, LDC and 39 of FPGA 190B (FIG. 7) in control of digital resistor 288 with output via lead 289, the speaker phone out lead 284 goes to the like connection in FIG. 14. A pair of audio amplifiers 290 and 292, Motorola Type MC 341190, operate in parallel and receive input of L1 TR input 208 (FIG. 9) and front panel audio on lead 294. The amplifiers 290 and 292 generate outputs consisting of speaker out 1 and speaker out 2 with a speaker enable output on lead 296. A transistor switch 298 controls operation of the circuit under influence of a MON EN or monitor enable input at terminal 300 as received from I/O port A8 of FPGA 190B (FIG. 7). 
     The circuit of FIG. 16 controls the application of power to the speaker phone circuits as leads 302, 304 and 306 are energized by L1 SEL, L2 SEL and SP EN energization from the FPGA 190A (FIG. 7) from respective gate ports I/O-A2, I/O-A15, and I/O 37. L1 RING and L1 TIP from leads 204 and 202 on FIG. 9, are applied to a telephone switch 306 to place L1 onto the speaker phone circuit. Alternatively, L2 may be selected via input 304 to latch speaker phone switch 310 and, in either event, signal on lead 312 causes switch 314 to latch in response to input of SP EN on terminal 306. Switch 314 functions as a hook switch for the speaker phone to provide indication through a transformer 316 and bridge circuit 318 to produce SP-C1 and SP-C2 outputs via leads 274 and 276 back to FIG. 14. The diode bridge 318 allows power supply board connection to power the speaker phone. 
     FIG. 17 is the system data acquisition circuitry which consists of an eight channel analog to digital converter, Maxim Type MAX180. The analog to digital converter 320 receives analog input (AIN) on lead 322 of the LCD light level sensor 324, the ambient temperature on lead 326 from thermistor 328, the charge level of batteries on leads 330 and 332 and the microphone audio output on lead 334 from microphone 336. The various data are converted to eight bit binary digital data on leads D0-D7 (A2D-D0 through A2D-D7) which are then conducted to designated gate ports on FPGA 190A. The remainder of the A2D digital outputs from converter 320 are then applied to ports on FPGA 190B. In addition to the sensed analog inputs AIN0-AIN4, the circuit 320 also receives an external analog input at AIN5 as well as L2TR and L2TR (AIN6 and AIN7) from FIG. 9. 
     FIG. 18 is a digital to analog converter 340 which receives digital signals on the left side from the FPGA arrays 190B and 190C. Thus, the D2A control outputs are connected from selected ports of FPGA 190B while the binary digital signals D2A 00 through D2A 07 are derived from ports on FPGA 190C. Analog outputs consist of lead 285 (FIG. 15) which conducts the D2A SPKR signal and the B output lead 272 which conducts D2A SP speaker phone output as utilized in FIG. 14. 
     FIG. 19 illustrates yet another digital to analog converter 342, Maxim Type MAX506, which receives binary digital output D0-D7 from a digital data bus 344 from FPGA 190A, ports I/O DIN-I/O D7. These digital inputs are under control of analog control signals A01 and A00 from FPGA 190C (FIG. 7) and write input D2A2 --  WR executes to provide analog outputs 344 conducting CTRLV CONTRAST to FIG. 13, and leads 346 and 348 conducting the caller number delivery V1 and V2 data to the caller number delivery modem 238 in FIG. 10. 
     FIG. 20 illustrates the power supply and energy management unit of the present invention. A Maxim Type MAX699 solid state device 350 receives input of -DACK1 on a lead 352 which triggers device 350 to produce RST output on lead 354 and a POWER GOOD indication on output lead 356. Amplifiers 358 and 360 are controlled by -IO WRITE input on lead 362 or -IO READ on lead 366 to produce outputs on the common lead 368 for input to the DS port of a solid state device 370. Solid state device 370 is a Chips and Technologies Type DQ2001 that functions as an energy management unit. 
     Battery input 372 from a rechargeable battery pack (if used) is applied through the circuit to the output lead 374 which is also tied back to the input port SR of device 370. The normal battery power, a rechargeable nickel-cadmium 12-volt pack having capacity of 1200 milliamperes, is connected for input at lead 376 and applied to a digital switch 378 as well as the SB port of device 370. The FET device 378 switches on and off to control charging of the battery pack. An FET 380 acting as a digital switch also functions in the battery charging process. A sensed temperature indication is input on lead 382 to the TS/VPP port of device 370 and the PWRON indication is input on lead 384 to the PS port. 
     The leads 386 are address and data signal inputs from the microprocessor 50 (FIG. 3) and the VBACK1 input relates to a backup battery that is not presently in use. The ports CPC, CPD, CC and CD of device 370 contribute to the battery charging operation through the FET switches 378 and 380. 
     The plurality of ports PO1 through PO6 relate to the various voltage supplies that are distributed throughout the circuitry in such manner as to save power wherever possible. It is extremely important to use a given segment of the power output for only specific purposes and for limited lengths of time in order to best economize power. 
     The present data terminal represents a next generation of the original DataStar™ telephone desk set as developed by the present assignee. The present data terminal is fully compatible with all existing applications and it meets exacting criteria in that data terminal 10 is based upon a 16-bit compatible processor running at 14 megahertz and is fully compatible with MS-DOS 5.0, thus allowing for development of custom application programs on a common platform. The data terminal display consists of a 320 X200 LCD backlit display of the transflective type, and the circuitry includes automatic light and temperature sensing circuitry in order to eliminate the need for most user adjustments while also enabling a great savings in precious battery power. 
     The terminal normally includes 1024 kilobytes of standard random access memory; however, this memory may be expanded to a total of 4 megabytes. The device is fully compatible with the 7970A printer, and upgrades and enhancements to the base product may be made readily by the user by dial-up connection to obtain software data. The data terminal is fully weatherproof and designed to operate in the most harsh environmental conditions that might be encountered in the field. A hermetically sealed housing or container protects the electronics against any of driving rain or liquid spills or submersion. The modem capabilities of data terminal 10 are greatly enhanced over prior types of similar equipment. The Z-note form factor allows for field installable modems with speeds up to 14,400 baud, employing MAP 2-5 and V.42 bis standards. The inclusion of Personal Computer Memory Card International Association interface allows expansion to a wide range of new RAM card technologies. 
     The present data terminal includes an expanded number of telephone/test set functions. The device has caller number delivery (CND) and supports the caller I.D. data interface specified in certain of the Bellcore documents, and a custom application program is available from the assignee to test this class feature. The system is capable of precision tone generation and subscriber line voltage measurements may be performed to within 15 millivolts accuracy. The terminal is equipped with an amplified loud speaker circuit that provides a high-impedance monitor for subscriber lines, this feature is enabled directly from the keyboard. Both telephone lines of the terminal employ software switchable circuits that allow placing a caller on hold or bridging circuits to conference capability and the system is able to generate and decode DTMF signalling. &#34;Hands-free&#34; amplified speaker telephone is provided with the data terminal as it automatically selects and connects to a line with available dial tone. 
     Changes may be made in the combination and arrangement of elements as heretofore set forth in the specification and shown in the drawings; it being understood that changes may be made in the embodiments disclosed without departing from the spirit and scope of the invention as defined in the following claims. ##SPC1##