1. Introduction
   
2. Initializing
   
3. Programming the Controller
   1. Programming the Timers
   2. Programming the CW Messages
   3. Programming the Flag Bits
   4. Programming the Courtesy Tones
   5. Previewing Stored CW Messages

4. Operating
   1. Enabling/Disabling the Repeater
   2. Using the NHRC-DAD Digital Audio Delay with the NHRC-4 Repeater Controller

5. Programming Example

• Configuration Flag Bits
• Message Numbers
• Morse Code Character Encoding
• Programming Memory Map
• Timer Address and Resolution
• Default Courtesy Tones Table
• Half Courtesy Tones
• Operational Modes

1. Introduction
   The NHRC-4 has 2 radio "ports", which are connectors that the radios connect to. There is a "primary" and a "secondary" radio port.

   The "primary" radio port is where the "main" repeater connects. All DTMF commands must come from here. When the primary radio is disabled, the secondary radio is also disabled.

   The "secondary" radio port is where the secondary radio connects. The secondary radio can be a remote base, link radio, or a second repeater, which when activated, is "married" to the primary repeater. The secondary radio can be disabled without any effect on the primary radio. No DTMF commands are accepted from this port.

   The secondary radio can be a "Remote Base," which is a simplex radio connected to the repeater system that allows the repeater users to remotely operate on a different frequency/mode/band than the repeater.

   The secondary radio can be a link radio to interconnect the repeater on the main port to a distant repeater. The link radio can be simplex or full-duplex. In the case of a full-duplex link, the main receiver and the link receiver can be repeated over both transmitters simultaneously. A simplex link will always transmit when the main receiver is active, potentially blocking any traffic that might be received over the link at that time.

   The secondary port can be connected to a repeater which will "marry" or "slave" to the main repeater. Anything received on either repeater will be re-transmitted by both repeaters. This allows repeaters on two different bands to be easily and inexpensively linked.

   The secondary port has several different modes of operation that apply to some or all of the applications described above. The secondary port's modes can only be selected by sending DTMF to the receiver connected to the primary radio port. These modes are:

   • disabled
   • alert mode
   • monitor mode
   • transmit mode

   In disabled mode, the secondary radio port is ignored by the controller.

   Alert Mode is a mode in which a different courtesy tone will be played if the receiver on the secondary port is unsquelched when the courtesy tone is requested. This is useful to indicate that traffic exists on a remote base frequency without having to hear the remote base traffic being repeated.

   In monitor mode, the secondary radio's receiver audio is retransmitted over the primary repeater, but the secondary port is inhibited from transmitting. This mode is also useful for remote base operation and monitoring linked repeaters.

   In transmit mode, the secondary radio's receiver audio is retransmitted by the primary radio, and the primary radio's audio is transmitted over the secondary radio. This mode is useful for remote bases, linked repeaters, and married repeaters.

   A married repeater requires that the controllers "secondary port is a duplex repeater" option be set. This option changes how the PTT line to the secondary radio port operates. Normally, the secondary radio port's PTT line follows the primary radio port's CAS (receiver active) line, that is the secondary port transmits when enabled and the primary receiver is active. When the "secondary port is a duplex repeater" option is set, the secondary radio port's PTT line follows the primary radio port's PTT line, so that the courtesy tone and tail are transmitted on the married repeater.

   The controller's programming is protected from unauthorized access by a 4-digit secret passcode. The controller is programmed by 8-digit DTMF commands that all begin with the 4-digit passcode. Throughout this manual, commands will be shown as ppppNNNN, where pppp represents the passcode, and NNNN is the actual command to the controller.

   In order to save space in the microprocessor memory, the NHRC-4 repeater controller represents all numbers in "hexadecimal" notation. Hexadecimal, or "hex" for short, is a base-16 number format that allows a 8-bit number to be represented in two digits. Hex numbers are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F. Converting decimal (the normal base-10 numbers that 10-fingered humans prefer) to hex is simple. Divide the decimal number by 16 to get the 1st hex digit (10=A, 11=B, 12=C, 13=D, 14=E, 15=F), the remainder is the 2nd hex digit. For example, 60 decimal = 3 x 16 + 12 = 3C hex. Any decimal number from 0 to 255 may be represented in only 2 hex digits.

   Many scientific calculators can convert between these two number systems, and the Windows 95 calculator can, too, if the "scientific" view is selected. We provide a WWW page that can generate all the programming data for the NHRC-4 controller quickly and easily, see http://www.nhrc.net/nhrc-4/nhrc4prog.php.

   A 16 key DTMF pad has keys 0-9 and A-D, which map directly to their corresponding hex digits. Use the * key for digit E and the # key for digit F. A 16-key DTMF pad is required to program the controller.

   Note that all programming of the NHRC-4 must be transmitted to the radio attached to the primary radio port.

2. Initializing the Controller
   The controller will need to be initialized to allow you to set your secret passcode. Initializing the controller also resets all programmable settings to the factory defaults, including the CW ID message. It should not be nessecary to initialize the controller again, unless you want to change the passcode. The only way to change the passcode is to initialize the controller.

   To initialize the controller, remove power and install the init jumper (JP3). Apply power to the controller, and after a few seconds, remove the init jumper. The controller is now in the initialize mode. If you "kerchunk" the primary port's receiver now, it will send the default CW ID of "DE NHRC/4". Now transmit (into the primary receiver) your 4-digit passcode. The controller will respond by sending "OK" in CW once. The controller will store the passcode and the main repeater will be enabled.

3. Programming the Controller

   All programming is done by entering 8-digit DTMF sequences. The first 4 digits are the passcode chosen at initialization. The next 2 digits are an address or a function code. The last 2 digits are the data for address or function. To enter programming information, you must key your radio, enter the 8 digits, then unkey. If the controller understands your sequence, it will respond with "OK" in CW. If there is an error in your sequence, but the passcode is good, the controller will respond with "NG". If the controller does not understand your command at all, it will not respond with anything other than a courtesy beep, and then only if the courtesy beep is enabled. If the controller is disabled, and an unrecognized command is entered, no response will be transmitted at all.

   Responses to Commands

   Response	Meaning
   "OK"	Command accepted
   "NG"	Command address or data is bad
   courtesy beep or nothing	Command/password not accepted

   
   If you enter an incorrect sequence, you can unkey before all 8 digits are entered, and the sequence will be ignored. If you enter incorrect address or data values, just re-program the location affected with the correct data.
   1. Programming the Timers
      The NHRC-4 Repeater Controller provides several timers which control the operation of your repeater. The Hang Timer controls how long the repeater will continue to transmit after a received signal drops. This is often called the repeater's "tail." The tail is useful to eliminate annoying squelch crashes on users' radios. As long as a reply is transmitted before the hang timer expires, the repeater will not drop, which would cause a squelch crash in the users' radios.

      The Timeout Timer controls the maximum duration of the retransmission of a received signal. It is more of a safety measure to protect the repeater from damage than a way to discourage long-winded users, even though it is often used that way. The NHRC-4 has a separate timeout timer for each port. The timeout timer(s) can be disabled by programming a 0 length.

      The ID Timer sets the maximum duration between transmissions of the repeater's ID message(s). (Note that the NHRC-4 may transmit an ID message before the timer expires in order to avoid transmitting the ID message while a user is transmitting.)

      The timer values are stored as an 8-bit value which allows a range of 0 to 255. Some of the timers require high-resolution timing of short durations, and others require lower resolution timing of longer durations. Therefore, timers values are scaled by either 1/10, 1, or 10 seconds, depending on the application.

      Timer Address and Resolution

      Timer	Address	Resolution Seconds	Max. Value Seconds
      Hang Timer	03	1/10	25.5
      Primary Receiver Timeout Timer	04	1	255
      Secondary Receiver Timeout Timer	05	1	255
      ID Timer	06	10	2550
      Fan Timer	07	10	2550

      Enter the 4-digit passcode, the timer address, and the timer value, scaled appropriately. For example, to program the Hang Timer for 10 seconds, enter pppp0364, where pppp is your secret passcode, 03 is the hang timer address, and 64 is the hexadecimal value for 100, which would be 10.0 seconds.

   2. Programming the CW Messages
      CW messages are programmed by storing encoded CW characters into specific addresses in the controller. Use the Morse Code Character Encoding table and the Programming Memory Map to determine the data and address for the CW message characters. For example, to program "DE N1KDO/R" for the CW ID, you would use the following commands:

      DTMF Command	Address	Data	Description/Purpose
      pppp2609	26	09	D
      pppp2702	27	02	E
      pppp2800	28	00	space
      pppp2905	29	05	N
      pppp2A3*	2A	3E	1
      pppp2B0D	2B	0D	K
      pppp2C09	2C	09	D
      pppp2D0#	2D	0F	O
      pppp2*29	2E	29	/
      pppp2#0A	2F	0A	R
      pppp30##	30	FF	End of message marker

      
      The CW ID can store a message of up to 20 characters. Do not exceed 20 characters. Be sure to include the end-of-message character (FF) at the end of each message.

   3. Programming the Flag Bits
      Controller features can be enabled with the use of the Configuration Flag Bits. These bits are encoded in a single byte, which is programmed into the controller at address 01. Multiple flag bits can be selected by adding their hex weights.

      For example, to set up a controller with an audio delay on each port, and configure the digital output for fan control, you would add 02, 04, and 10 to produce hex 16, which you would then program into address 01 in the controller with this command:
      

      pppp0131

      In addition to programming the flag bits as a group using address 01, the controller supports commands to set or clear these bits individually. Command 60 is used to clear (zero) a specified configuration bit, and command 61 is used to set (one) a specified configuration bit. For example, to set (turn on) bit 3 (to suppress DTMF muting), enter the following command: pppp6103. To clear bit 3 and enable the DTMF muting, enter this command: pppp6003. Note that the bit number, not it's hex weight is used for commands 60 and 61.

      Configuration Flag Bits

      Bit	Hex Weight	Binary Value	Feature
      0	01	00000001	secondary port is duplex repeater
      1	02	00000010	audio delay on primary receiver
      2	04	00000100	audio delay on secondary receiver
      3	08	00001000	disable DTMF muting
      4	10	00010000	digital output is fan control
      5	20	00100000	main receiver has priority over link receiver*
      6	40	01000000	drop main transmitter to mute DTMF**
      7	80	10000000	drop secondary transmitter to mute DTMF**

      *Software version >= 1.4 only.
      *Software version >= 2.2 only.

      Example Configurations

      Flag Bits Value	Features Selected
      00	none
      01	duplex repeater on secondary port
      08	no DTMF muting
      10	digital output is fan control
      11	duplex repeater on secondary port digital output is fan control
      17	duplex repeater on secondary port NHRC-DAD on primary port NHRC-DAD on secondary port digital output is fan control
      36	NHRC-DAD on primary port NHRC-DAD on secondary port digital output is fan control main receiver has priority over link receiver*
      1F	duplex repeater on secondary port NHRC-DAD on primary port NHRC-DAD on secondary port no DTMF muting digital output is fan control

      *Software version >= 1.4 only.

   4. Programming the Courtesy Tones
      The NHRC-4 uses up to five different courtesy tones to indicate various events:
      • primary receiver
      • primary receiver, the secondary transmitter enabled
      • primary receiver, alert mode
      • secondary receiver
      • secondary receiver, secondary transmitter enabled

      Each tone is individually programmable, and can be unique for that event, programmed to be the same as other events, or programmed empty to be silent.

      The NHRC-4 will play the appropriate courtesy tones 500 milliseconds (1/2 second) after a receiver drops. The courtesy tones all consist of four 100 millisecond (1/10 second) segments. Each segment can be no tone, low tone (a "boop", about 440 hertz), or high tone (a "beep", about 880 hertz). If all the segments are programmed as no tone, the courtesy tone will be disabled. The default courtesy tones are shown in the Default Courtesy Tones Table.

      Default Courtesy Tones

      Event	Default Tones	Binary Encoding	Hex Encoding
      Primary Receiver	beep none none none	00 00 00 01	01
      Primary Receiver Secondary Transmitter Enabled	beep none beep none	00 01 00 01	11
      Primary Receiver Secondard Receiver Alert Mode	beep none boop none	00 11 00 01	31
      Secondary Receiver	boop none none none	00 00 00 11	03
      Secondary Receiver Secondary Transmitter Enabled	boop none boop none	00 11 00 11	33

      The courtesy tones are encoded as four pairs of bits, with the first segment encoded as the two least significant bits, and the fourth segment encoded as the 2 most significant bits. Each pair of bits is allowed three possible values to indicate no tone, beep, or boop. The Half Courtesy Tones table shows tones generated for valid 4-bit values and their hex representation. To use this table, first determine the tones for each of the four segments, then find the hex digit that represents the first and second pair of tones. The second pair's digit becomes the first hex digit, and the first pair's digit becomes the second hex digit. For example, to encode a courtesy tone of boop-beep-boop-none, you would find the first pair (boop-beep) in the table as the hex digit D and the second pair (boop-none) in the table as the hex digit 3, so your courtesy tone would be encoded as 3D.

      Half Courtesy Tones

      Tones	Binary Encoding	Hex Encoding
      none none	00 00	0
      none beep	01 00	4
      none boop	11 00	C
      beep none	00 01	1
      beep beep	01 01	5
      beep boop	01 11	7
      boop none	00 11	3
      boop beep	11 01	D
      boop boop	11 11	F

   5. Previewing Stored CW Messages
      Stored CW messages can be previewed with the command 40 followed with the message number you want to preview. The message numbers can be found in the Message Numbers table. For example, to preview the secondary receiver timeout message, send command:
      
      pppp4004

4. Operating
   
   1. Enabling/Disabling the Repeater
      The radio ports can be disabled or enabled by remote control by setting the code for the operational mode in location 00. See the Operational Modes Table for the codes that indicate the mode you want.

      Operational Modes

      Code	Operational Mode
      00	Primary & Secondary off
      01	Primary enabled
      02	Primary enabled, secondary alert mode
      03	Primary enabled, secondary monitor mode
      04	Primary enabled, secondary transmit mode

      For instance, to disable the repeater, send command:
      

      pppp0000
      
      To enable the repeater on the primary port, send command:
      
      pppp0001
      
      To enable the repeater on the primary port, and select monitor mode for the secondary port, send command:
      
      pppp0003

   2. Using the NHRC-DAD Digital Audio Delay with the NHRC-4 Repeater Controller.
      The NHRC-4 Repeater Controller supports the optional NHRC-DAD digital audio delay board. The NHRC-DAD allows complete muting of received DTMF tones (no leading beep before muting), and suppression of squelch crashes when the received signal drops. The NHRC-DAD has a 128 ms delay on all received audio. The NHRC-4 Repeater Controller supports a NHRC-DAD on both radio ports with a software switch and a dedicated DAD connector for each port. If the DAD is not present, then a jumper must be installed between pins 2 and 3 of the DAD connector (see installation manual). If the DAD is present, then the appropriate configuration flag bit must be set.

5. Programming Example
   Programming the NHRC-4 Repeater Controller can seem quite complicated at first. This section of the manual is intended as a tutorial to help you learn how to program your controller.

   Let's assume we want to program a NHRC-4 Repeater Controller with the following parameters:

   CW ID: DE N1LTL/R FN42
   Hang Time 7.5 seconds
   Timeout timer 120 seconds
   

   First, we will initialize the controller. Install JP3 and apply power to the controller to initialize. After a few seconds, remove JP3. Send DTMF 2381 to set access code to 2381. The controller will send "OK" in CW to indicate the passcode was accepted. Now the controller is initialized, and disabled.

   Now we will enable the controller. Send DTMF 23810001 (passcode=2381, address=00, data=01). The controller will send "OK" in CW to indicate the command was successful.

   We will now program the CW ID. Looking at the "Programming Memory Map", we can see that the first location for the CW ID is 26. The first letter of the ID is 'D', which we look up in the "Morse Code Character Encoding" table and discover that the encoding for 'D' is 09. Location 26 gets programmed with 09.

   Send DTMF 23812609 to program the letter 'D' as the first character of the CW ID. The controller will send "OK" in CW if the command is accepted. If you entered the command correctly, but you don't get the "OK", your DTMF digits may not all be decoding. See the Installation Guide for your controller to readjust the audio level for the DTMF decoder.

   The next character is the letter 'E', which is encoded as 02, and will be programmed into the next address, 27. Send DTMF 23812702.

   The next character is the space character, and it will be programmed into address 29. Send DTMF 23812800. Here are the rest of the sequences to program the rest of the ID message:
   

   23812905 (N in address 29)
   23812A3* (1 in address 2A)
   23812B12 (L in address 2B)
   23812C03 (T in address 2C)
   23812D12 (L in address 2D)
   23812*29 (/ in address 2E)
   23812#0A (R in address 2F)
   23813000 (space in address 30)
   23813114 (F in address 31)
   23813205 (N in address 32)
   23813330 (4 in address 33)
   2381343C (2 in address 34)
   238135FF (EOM in address 35)
   

   After the last character of the CW ID is programmed, the End-of-Message character must be programmed. In this case, the last character of the ID message was programmed into address 34, so the EOM character, which is encoded as FF, goes into address 35:
   238135## (EOM into address 35.)

   To program the hang timer, we must first determine the address of the hang timer by consulting the Programming Memory Map. The Hang Timer preset is stored in location 03. Next, we need to convert the 7.5 seconds into tenths, which would be 75 tenths of a second. Then the 75 gets converted to hex:
   

   75 / 16 = 4 with a remainder of 11, so 75 decimal equals 4B hex.

   Now program the hang timer preset by sending 2381034B.

   To program the primary receiver's timer with 120 seconds, we get the address of the primary receiver's timeout timer preset, which is 04, and then convert 120 seconds to hex:
   

   120 / 16 = 7 with a remainder of 8, so 120 decimal equals 78 hex.

   So we will program location 04 with 78: 23810478

   Any CW message can be played back at any time by "programming" location 40 with the message code you want to play. To play the CW ID, send 23814000.