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Build a multi-sector burglar alarm, Pt.2 Last month, we described the features of this versatile home burglar alarm & gave the circuit details. In this article, we show you how to build & operate it. By MIKE ZENERE Because it's built around a microprocessor and relies on software , the circuit uses relatively few components for such a versatile unit. In fact, by making some slight software changes, two more features have been added to the unit since last month. First, the user can now select whether or not power is maintained 22 SILICON CHIP to the remote keypads during a mains failure. Previously, the user had no choice; if the mains failed, the remote keypads could not be used and the backup battery only supplied power to the main keypad. You can now elect to maintain power to the remote keypads, although this will decrease the battery back-up time. Second, the user can now select whether or not the unit beeps when an entry is detected, prior to sounding the main alarm. If you're the sort of person who always remembers to turn an alarm off, the warning beeps can be disabled. The choice is yours. There's also been a slight change to the main circuit (Fig.2) that was published last month. First, a larger relay with higher-rated contacts has been substituted for the original unit and this has necessitated the addition of a simple 1-transistor driver circuit- see Fig.5. Second, a LED (LED 1) and a lkQ series resistor has been connected to pin 28 of ICl. This LED is used to confirm that the oscillator based on IC2e is operating correctly before the MCU (!Cl) is plugged in, but otherwise plays no part in the circuit operation. The necessary changes have been made to the relevant PC board. Most of the assembly simply involves installing parts on the PC boards; there is very little interboard wiring involved: However, it is important to follow the procedure outlined below, as certain sections are assembled and tested before moving on to the next stage. Processor board assembly Construction begins with the processor board (Fig.6) and its numerous individual circuits. First, install all the links, PC pins and terminal blocks. This done, install the following parts: BRl, Cl, C2, C31, C32, Rl, R2, R3, R8 (mounted 10mm above the board), D17, ZD4, D2, D3, D16, FCl, FC2, FC3, FC4, FC5, FC6, FUSE 1, FUSE 2 & FUSE 3. When all these parts are in, attach REGl and REG2 to their heatsinks as shown in Fig. 7 and then mount the two regulators on the board (be careful not to transpose them). You are now ready to test the power supply circuit. To do this , connect the 16VAC plugpack supply to the board with a l0Q 1W resistor in series with one of its leads. This resistor will limit the current if there is. a short on the board. Apply power and check for the following DC voltages: (1). Positive terminal Cl = 20V (approx). (2). Output of REGl = 5V. (3). Output of REG2 = 15V. (4). Pin 7 ofTBl = 15V. (5). Pins 3, 6 & 7 of ICl = 5V (6). Pin 14 of IC2 = 5V. (7). Pin 20 of IC3 = 5V. (8). Pin 14 of IC4 = 5V. If all of the above are OK, switch off the power and install R3, R4 (mounted 10mm above the board), R5-R13 (but not R8), R20-R22, R62-R65, C6, C7, Ql-Q4, Qll, Q12, Dl, D4-D8, ZD3 and the battery leads. Now install temporary links between (1) the +5V output ofREGl and the anode ofD4; and (2) the output of REGl and pin 19 of ICl. This will enable you to check the battery charge circuit. Apply power and check for the following voltages: (9). Positive lead of battery= 14V (approx). (10). Voltage across R4 = 0V. (11). Collector ofQl = 19V (approx). (12) . Cathode of ZD3 = 14V (approx) . r-------.-+12V 013 PN200 Fig.5: the modified relay driver circuit. The circuit is driven by the PB5 output (pin 17) ofICl. (13). Collector of Q4 = 0V. (14). Pin 1 of TB3 = 15V (approx). Now connect the leads to the battery with your multimeter in series with one leg of the circuit and check the charging current. It should be somewhere between 0mA and 35mA. If this checks out, remove the meter from the circuit, reconnect the battery and check that the following voltages are correct: (15). TBl pins 11 and 12 = 12V. (16). Output terminal of REGl = 5V. (17). Pin 7 ofTBl = 12V. (18). Pin 1 TB3 = 12V. Assuming these values are OK, remove the 5V temporarily applied to G) Fig.6: parts layout for the processor board. It should be assembled & tested exactly as described in the text. OCT0RER1992 23 HEATSINK 10220 DEVICE NUT ~ ~ i l SIL;AD ~ SCREW j lllIIlllI{3 Fig.7: attach REGt & REG2 to their heatsinks as shown in this diagram. The "silpad" is there to aid heat transfer. D4 and pin 19 ICl and do the following checks: (19). Collector ofQ3 = 12V (approx). (20). Collector-emitter voltage of Q2 = 1V (approx). (21). Voltage across R4 = llV (approx). (22). Pin 1 TB3 = 0V. If all of the above are correct, switch off, remove the temporary links, and corn plete the board assembly. A socket is used for ICl but before this is soldered in, make sure that D4 is in place, as it sits under the socket. Display board assembly Fig.8 shows the assembly details for the display board. Initially, all of the parts can be soldered into place, except for the display and the three ICs. Note that the beeper (BEEPl) is soldered to the copper side of the board and that the LEDs should all be mounted above the board so that they will later protrude through the front panel - see Fig.9. Check that all LEDs are correctly oriente::d; the anode lead is always the longer of the two. The keypad is mounted flush against the board by removing its mounting tabs and securing it with a small amount of adhesive . Short lengths of tinned copper wire are then used to make the connections. This done, locate the two 16-way IDC connectors and crimp both plugs on to the ribbon cable as shown in Fig.10. Make sure that pin 1 of the first connector is terminated to pin 1 of the second connector, as a wrong termination will cause disaster on the display board. The two IDC connectors can now be soldered to the processor and display boards. Now power up and check for 5V at the following points on the display board: pin 8 ofJl ; pin 20 oflC1 & IC2; and pins 3, 5, 9 & 18 of DISPl. If all is OK, switch off and solder in the ICs and the display, noting that pin 1 of this device is as shown in Fig.11. Be careful - there are no second chances with this chip. Before plugging in the MCU, it's advisable to take a few extra moments to test the rest of the circuit. To do this , first install lOkQ resistors between the 12V outputs ofTBl and the siren and strobe light outputs. This done, install a lOkQ "end-of-line" re- sistor on each of the sector inputs (ie, between each sector input and the input ground). Apply power and check the following on the processor board: (1). LED 1 should be flashing on and off at around 2Hz. (2). Pin 2 of ICl should have a waveform on it of 50Hz at 2V p-p (check using an oscilloscope), while pin 6 of IC2 should be oscillating at a high frequency. (3). Pins 3, 4, 10 & 11 of IC4 should all be at 5V. Now short out all four of the lOkQ end-of-line resistors in turn and check that pins 3, 4, 10 & 11 of IC4 are all at 0V. If one of the outputs does not go to 0V, check the circuitry around the relevant gate carefully. If everything is OK, remove the shorts from the resistors. Installing the MCU Switch off the plugpack and make sure that the battery is disconnected. You are now ready to plug in the MCU (ICl) but make sure that it is correctly oriented. Apply power again and check that the reset status LED (LED 1) now stays on. If it does, this indicates that the processor is correctly servicing its interrupt routine once every 20ms. At the same time , the alphanumeric display on the display board should flash the message "UNIT OK", while all the LEDs on this board should be off. If the reset status LED continues to RESISTOR COLOUR CODES I I I I 24 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 No. Value 4-Band Code 5% 5-Band Cod_ e (1%) 1 2 1 1 8 2 8 23 3 11 7 1 14 1 1 1 1 1 820kQ 470kQ 220kn 180kn 150kQ 100kQ 75kQ 68kQ 47kQ 10kQ 4.7k.Q 1.5k.Q 1k.Q 270Q 100.Q 33Q 15Q 3.9Q grey red yellow gold yellow violet yellow gold red red yellow gold brown grey yellow gold brown green yellow gold brown black yellow gold not applicable blue grey orange gold yellow violet orange gold brown black orange gold yellow violet red gold brown green red gold brown black red gold red violet brown gold brown black brown gold orange orange black gold brown green black gold orange white gold gold grey red black orange brown yellow violet black orange brown red red black orange brown brown grey black orange brown brown green black orange brown brown black black orange brown violet green black red brown blue grey black red brown yellow violet black red brown brown black black red brown yellow violet black brown brown brown green black brown brown brown black black brown brown red violet black black brown brown black black black brown orange orange black gold brown brown green black gold brown orange white black silver brown SILICON CHIP ~ --ao- G r--7 r--7 -aa- c,::= IC3 --aD---CID------CBD--- L.f"'W ; L.f"'W LEm ® LED2 ® . cs::= [ L[D3 ® LED4 ® LEDS ® KEYPAD! LED8 ® N□ T USED LJ Fig.8: the display board accommodates the keypad, the alphanumeric display & a handful of other parts. Jl accepts one end of the 16-w ay header plug. flash , ch eck the watch dog circuit for mistakes. If none are foun d , you can temporarily disable th e watch dog circuit by placing a lkQ resistor in parallel with R14. This will cause the processor to come out of the reset state and you w ill be able to test for th e fo llowing: (1) . On th e processor board: (a) continuous data on pins 8-1 1 and 20-2 7 of the MCU; and (b) data on pin 19 of IC3. (2) On the display board: (a) data on pins 2-9 and 11 ofICl an d IC2; an d (b) data on pins 1, 2, 6 -8 and 11-17 of DISP1. . Mounting the boards The two PC boards can n ow be in stalled in the case. This is suppli ed pre-pu nched for easy assembly. First , peel the backing off th e label and carefu lly affix it to the front panel. Th e display board is now mounted on th e back of th e li d on 6mm standoffs and secured using seven M3 x 5x5mm LEDS Fig.9: mount the LEDs on the display board exactly as shown here, so that they later protrude through the 'front panel by the correct amount. Kit Availability A complete kit of parts for the home burglar alarm is available from the author. This kit includes all elec. tronic components, the PC boards, a pre-punched case with the front sticker, mounting hardware , a 16VAC plugpack supply, and the 12V 2.6Ah battery (remote keypads not included). The price is $195 plus $16 p&p, or$175 plus $16 p&pwithout the case. Kits for the remote keypads are available at $44 each (includes all parts) . Completely assembled and tested units are also available. These are priced at $240 for the alarm panel and $50 each for the remote keypads. What if you can't get it going? If that happens, the PC boards only can be returned to the author, along with a cheque for $35 to cover the cost of repair. This fee covers return postage, labour and all parts except for the microprocessor. The author reserves the right to return any boards and the repair fee if the boards have been so badly assembled as to make repair too difficult. The following accessories are also available (prices include p&p). Passive infrared detectors (1) Rokonet 3001 PIRO, 64 x 44 x 35mm-$65. (2) Rokonet 6000 PIRO, 105 x 65 x 46mm-$72. Glass breakage detectors (1) C+K OualTec, 7.6-metre range, 95 x 62 x 19mm -$70. (2) C+K FlexGaurd, 4.5-metre range, 98 x 61 x 20mm - $63. Miscellaneous Horn speakers- $12. Strobe light - $25. Piezo siren - $17. 4-core cable (for PIROs), 100metre roll - $42. Figure-8 cable (for strobe light, siren , etc), 100-metre roll - $20. HPOL 2416 alphanumeric display - $16. Please make cheques payable to Michael Zenere, 7 Hayfield Rd, Mt Waverley, Victoria 3149. Telephone (03) 803 1831. Allow up to 15 working days for delivery. Alternatively, kits and assembled units may be purchased directly from the above address. Note: copyright of the PC artworks associated with this project is retained by the author. OCTOBE R1 992 25 and solder one lead of each LED only. This done, remove the cardboard and align the LEDs before soldering the remaining leads. The second line of LEDs can now be installed in the same manner. Once the LEDs are in, the remaining parts can be installed on the board. Bend the leads of the regulator (REG1) so that it lies flat against the PC board (see photo). A 28 -pin socket is used for the MCU (IC1) but don't insert the IC just yet. Note that because parts must be mounted under the IC, the socket will have to be cut into two single rows - see Fig.12. The wiring can now be completed by running seven 8cm-long leads between the board and the keypad. The eighth terminal on the keypad (adjacent to the "3" button) is not used. Remote keypad testing Take great care with the orientation of the alphanumeric display (DISPl) when installing this part on the PC board (see Fig.11). The keyboard is secured to the PC board by its connecting links & a small amount of adhesive. 12mm countersunk screws and nuts. This job will be easi er if you install the middle standoff and mounting screw assembly first. The four 10mm tapped standoffs are used to mount the processor board on the rear panel and are secured to the case using four M3 x 6mm countersunk screws. This done, use four M3 x 6mm panhead screws to secure the board to the spacers, then install the 6.5mm rubber grommet in the power entry hole. Run the plugpack cable through this grommet, clamp the cable so that it cannot be pulled out, and solder the wires to the PC pins. Finally, attach the battery leads to the battery and close the lid. Keypad construction Fig.12 shows the assembly details 26 SILICON CHIP for the remote keypads. Start the assembly by installing the parts that go under the MCU. These include the crystal (XTALl), resistors R7, RB & R9, and capacitors C3 & C5. When this has been done, the seven LEDs can be installed. These are in two rows. The top row consists of three LEDs and these are, from left to right: green, orange and red. The bottom row, from left to right, consists of three orange LEDs and one red LED. The LEDs must all be mounted exactly 15mm above the board (ie, so that their tops are about 20mm above the board). To do this, cut a 15mm wide cardboard strip about 40mm long and thin enough to fit between the legs of the LEDs. Position this strip of cardboard edge-on along one line of LEDs, then install the LEDs over it At this stage, it is a good idea to do a preliminary test of the board. This is done by applying 10-15V to the terminal block and checking for the following voltages : (1). Pins 3, 6 & 7 of IC1 = 5V. (2). Pins 1 & 2 of IC1 = 0V. (3). Pins 20, 21 & 22 of IC1 = 5V. If these checks are OK, disconnect the power and install IC1. Now reapply power and check that the green LED lights (all other LEDs off). Testing of the keypad is now complete and the unit may be installed in its plastic case. The plastic case is supplied partially drilled; all you have to do is make the hole for the keypad. This is quite straightforward since the shape of the hole· is scribed into the plastic on the inside of the lid. To make the hole, drill a series of small holes around the inside perimeter of the marked area, then knock out the centre piece and file for a smooth finish. The four 10mm tapped spacers can now be secured to the bottom of the case using M3 x 6mm countersunk screws - see Fig.13 . This done, attach the keypad (via its tabs) to the inside of the case using superglue (top towards the three LEDs) . Finally, secure the PC board to the spacers using four roundhead M3 x 6mm screws and clip the two halves of the case together. Setup & operation As well as turning the unit on or off, the front panel keypad is used to Introducing the Tektronix 2212 Value Priced at $345 0 * Real Analog - Real Digital Storage No Compromise ■ 60 MHz Bandwidth ■ Analog ■ Auto and Digital Storage Operation setup ■ 20MS/sec Maximum Digitizing Speed ■ On - Screen Parameter Readout ■ 4K Record Length ■ Parallel Printer Interface (STD) ■ 2 1Ox Probes Included ■ Fully Programmable via RS-232/GPIB (Opt) ■ 3 Year Warranty 0 For further information on Tektronix 2212 Portable Oscilloscope Call Toll Free (008) 023342 or contact your local Tektronix office. Tektronix /rest and Measurement Sydney (02) 888 7066 Melbourne (03) 836 3355 Brisbane (07) 394 1155 Adelaide.(08) 223 2811 Perth (09) 242 4688 Canberra (06) 251 6111 *Price does not include sales tax. 16-WAY JDC CONNECTOR 16-WAY IOC CONNECTOR PIN 1 Fig.10: wire the JDC pin connectors to the 16-way cable exactly as shown here. This cable connects the display board to the processor board. WRli~~~ :1~iNG-I HPOL2416 DISPLAY LX DL2416 I ,-;-'I,~1I~I1---,---11 PIN'-r--1 Fig.11: pin 1 of the HPDL2416 display is adjacent to the type number that's printed along one side. select, view and modify a number of variables, and to perform the various test functions. There are two main buttons used to call up the different options and these are the function button (*) and the return button (#). The 0-9 buttons are used in conjunction with the(*) button to select the variable to be viewed. At the very first power up , the on/ off code is set to 6805. This code will also allow you to modify the preset variables. These variables and their initial settings (in brackets) are listed in Table 1. Note that the variables are locked in and cannot be changed unless the user knows the current on/off code. This was done for obvious security reasons. The five locked codes are the entry delay, exit delay, siren duration , on/off code and the soft switches. Let's assume that the unit has never been powered up. In this case, all the sectors will all be off; the entry delay, exit delay and siren duration times will be set to 30 seconds, 3 minutes and 3 minutes respectively; the on/ off code will be 6805; and the soft switches will be set to 019X (ie, the keypads will be disabled during mains failure; the unit will beep on entry; and the alarm can sound up to 9 times in one 12-hour period). The user now can decide which options, if any, are to be changed. RU R16 RI:! <at>~-<at>O<at>O. 0 Once these are programmed in, you can forget about them unless of course you wish to change them again. In everyday use, you'll only change the sector settings and turn the alarm on KEYPAD ~ TERMINAL BLOCK 'i"' e_oA_R_□--~□~/-cASE _ P_c ! M3x10mm TAPPED SPACERS ~~ M3x5mm CSK SCREWS a Fig.13: this sectional view & the accompanying photo show the assembly details for the remote transmitter. The keyboard tabs are glued to the top of the case using a suitable adhesive. or off using the 4-digit code. The test function will also be used occasionally to check the siren, strobe light and on-board relay. In most cases, you can use the default settings although you will want to change the on/off code. To do this , press buttons (* ) (8), note that the display flashes ****• and enter the current code on/off (initially 6805). The display will now show the current code with the first digit flashing. Enter the new code (eg, 5739), then press the(#) key to store the new code and exit the code setting function. To show you how quick and easy the alarm is to use, let's assume that you wish to activate the alarm with sectors 1 and 2 on. We'll also assume that, initially, all sectors are off and that on/off code is 5739. The procedure is as follows: First, activate the two sectors by pressing(* ) (1) (2) (#) - the two LEDs TABLE 1: ALARM PANEL OPERATION Buttons Initial Status Function Instructions (*) (1) Sector 1 on/off switch Off Press (*) (1) (#) to toggle sector 1 on or off. (*) (2) Sector 2 on/off switch Off Press (*) (2) (#) to toggle sector 1 on or off. (*) (3) Sector 3 on/off switch Off Press (*) (3) (#) to toggle sector 1 on or off. (*) (4) (*) (5) (*) (6) Entry delay setting Exit delay setting Siren duration setting 30 seconds Press(*) (4). Display flashes to show current setting (first two digits= minutes; last two digits= seconds). To change, enter on/off code. Unit now flashes first digit. Enter new entry delay period (0959 max.) , then press (#). 3 minutes Press (*) (5) . Display flashes to show current setting (first two digits = minutes; last two digits = seconds). To change, enter on/off code. Unit now flashes first digit. Enter new exit delay period (0959 max.), then press(#). 3 minutes Press (*) (6) . Display flashes to show current setting (first two digits = minutes; last two digits = seconds) . To change, enter on/off code. Unit now flashes first digit. Enter new siren period (0959 max.), then press (#). Digit 1: Remote keypad on or off during mains failure 0 (Off) Digit 2: Beep on/off during entry delay 1 (On) (*) (7) (*) (8) (*) (9) (*) (0) Digit 3: Alarm lockout count 9 Digit 4: alarm tamper setting 1 On/off code setting Past status indication Test mode: (1) Siren test; (2) Strobe light test; (3) Relay test 6805 Press(*) (8) . Display flashes****. Enter current on/off code (initially 6805) . Unit now shows code with first digit flashing . Enter new code , then press(#). None If the alarm has sounded, the memory LED on the front panel will be on. Turn off the alarm & press (*) (9) - hold the (9) button down. The LED(s) for the sector(s) that tripped will come & the display will indicate how many times the alarm tripped (up to 99 times). This feature is useful for tracking down a sector that intermittently false triggers. II 11 Press (*) (7). Display now shows the current state of the three soft switches (initially 0191 ). To alter, enter the on/off code. Set the first digit to Oto disable the keypads during mains failure , or to 1 to maintain power during mains failure. Set the second digit to Oto disable the beeps during the entry delay, or to 1 to enable the beeps. The third digit designates the number of times the alarm is allowed to sound in one 12-hour period (range 1-9). Entering 0 allows the alarm to sound every time an intrusion is detected. Set the fourth digit to 0 so that the alarm is not triggered by cutting the siren or strobelight lines, or to 1 to trigger the alarm for one cycle if a line is cut. Press (#) when all settings are correct. Press (*) (0). The display flashes the word TEST to indicate the test mode. Hold down button (1) to test the siren (the display will flash the letters SIRN & the siren should sound); hold down button (2) to test the strobe light; hold down button (3) to test the on-board relay. Press (#) when testing is complete. General notes: (1 ). The alarm panel is turned on or off by entering the current 4-digit on/off code (sectors can be left on when alarm is off). ' (2). Variable settings can only be altered when the alarm panel is turned off & by entering the current on/off code . (3). If the on/off code is forgotten, it can be viewed as follows: (a) Remove battery power & then the AC power ; (b) Hold down the (1) key & apply AC power to the unit~(c) Release the (1) key & reconnect the battery; (d) Press (*) (8) - the display will now show the current on/off code; (e) Pr ss (#) to exit. After this, pressing(*) (8) will display the usual****. (4). If the function(*) key is pressed , the next key must be pressed within 5 seconds for the function to be selected. 30 SILICON CHIP associated with these sectors should light. Next, arm the alarm by pressing (5) (7) (3) (9) . The ON LED should light and, assuming that the default exit delay setting is unchanged, you now have three minutes to leave the house. To re-enter the house, you simply enter (5) (7) (3) (9) to turn the alarm off again before the entry delay period expires. The ON LED should now turn off but note that the sector LEDs remain lit unless you toggle the sectors off again. In most cases, you'll leave the sectors on, so that you don't have to activate them again the next time you leave the house. PLUG·PACK ,:]lr>-16VAC_ : :.r:-r BATTERY 12V 2.6A -"I'.._____!___ I I 12V HORN SPEAKER I I I 12V STBOBE LIGHT The location of the main alarm box will depend on whether or not remote keypads are used. If the remote keypads are not used, then the box must be accessible to the user, so that the alarm can be turned on and off. Even so, it should be mounted in a concealed area, such as a linen press or kitchen cupboard. The remote keypads should be mounted inside the premises, as they are not weatherproof. Fig.14 shows how external devices are connected to the processor board. Don't forget the end-of-loop resistors for the sector inputs (see Fig.1 in last month's issue). Fig.15 shows how up to two remote keypads can be connected to the system. In particular, note how TX on the remote keypads is connected to RX on the processor board and vice versa. Be very careful here - it's all too easy to get these connections mixed up . +12V1.5A SIREN DRIVER PROCESSOR PC BOARO STROBE LIGHT DRIVER (S) +15V 400mA s SECTOR 3 INPUT (I) GNO FOR INPUTS s 24 HOUR SECTOR INPUT (S) SECTOR 2 INPUT e GNO FOR INPUTS SECTOR 1 INPUTS ,Mif rt t~ 1 - - - - -- - - - - -cl:UJTs TO REMOTE KEYPADS Fig.14: follow this wiring diagram when linking external devices & peripherals to the processor board. Note that the sector inputs must be terminated using 1okn end-of-loop resistors, as shown last month in Fig.1. that the alarm still functions if the first is disabled by a determined thief. Generally, a horn speaker is mounted under the eaves inside a metal cover and this serves as the main siren. The second siren can be a piezo type and should be mounted out of sight in the roof cavity. Deciphering the beeps Finally, a word on deciphering the various beep signals from the unit. There are four different patterns: (1) the unit beeps once each time a key is pressed; (2) the main unit and remote keypads beep four times every second during the entry delay; (3) the main panel beeps three times if you try to enter an illegal setting; and (4) if there is a fault in the system, the main unit and remote keypads beep twice every 15 seconds. SC ·"' ~ ""LJ PROCESSOR PC BOARD TB3 [ (1) <]) - Passive infrared sensors A large range of passive infrared detectors (PIRDs) is available on the market and these can be purchased from about $50.00 upwards . However, some of the cheaper units are prone to false triggering, so it's worth paying a few dollars more for good quality sensors. The PIRDs listed in the panel are both very reliable units. When installing them, make sure that they do not face towards windows to avoid false triggering. They should also be positioned so that are not in a direct line with sunlight. It's also a good idea to have a second siren connected to the system, so 0 (I) (S) SECTOR INPUTS (SEE Fig. 1) Installation +12V1.5A Q) GNO FOR PERIPHERALS I PASSIVE INFRARED DETECTOR (SUPPLY CONNECTIONS ONLY) (l) ~~ 0 - - ALARM OK TO ON ENTERQ 0 QM EMORY 000 REMOTE KEYPAD 2 REMOTE KEYPAD 1 +15V OV TX RX - 1 ' ' I FAULT 9 0 0 DETECTED __J L_/~ SECTOR SECTOR SECTORQ 2 ~+15V :...-., r I l f\ I NOTXECTION RX TO TX, TX TO RX ov -Tx 'I RX 0000 3 Fig.14: connections between the remote keypads & TB3 on the processor board are run using 4-way cable. In particular, note how TX on the keypad boards connects to RX on the processor board & vice versa. The LED functions are indicated on the remote keypad at left. OCT0BER1992 31