2. OPERATIONAL OVERVIEW

There are many different aspects to the operation of the FF-800 repeater controller. The FF-800 carries a variety of configuration options as well as several interface options including: temperature sensing, input/output logic control, voter logic and CTCSS inputs, multiple DTMF command paths, and more. This chapter discusses the various operational characteristics of the FF-800 system and provides an overview of the commands and options available.

2.1 Transceiver Assignments

The FF-800 has five tx/rx ports including a local microphone port to interface to your repeater's RF system. The transceiver assignment options represent a unique combination of features. Each tx/rx port can be configured to operate in one of three modes: Main, Link, or Remote Base (the local microphone is fixed as a main port). Each configuration behaves somewhat differently, and these differences are described below:

In addition to defining the "personality" of each port, there is a user defined priority system that defines the priority level of each receive port in the system. In this system, the highest priority receive port that has activity is passed to the transmit side of the controller -- all lower priority receive ports are muted. There are no restrictions concerning how the priority progression is defined -- if desired, a remote base port can have a higher priority than a main port (though this would be unusual). The priority system continuously updates the switch status to reflect current receiver activity -- thus, if a port is active into the controller, and a higher priority port comes active, the higher priority port will be immeadiately passed to the transmit ports and the original port is muted.

A third feature that helps define the unique port structure of the FF-800 is the digital level controls that are present for each port. This allows the user to independently control the audio level of each receive input or transmit output in the system. This is especially helpful in linked systems where the controller may be remotely located from one or more link sites. If a change is made at one of the link sites that results in an audio level shift, the user has the ability to remotely compensate the audio level for that particular receive port. Also, the digital levels can be more precisely controlled than mechanical level controls and the digital controls are not subject to wear or corrosion as there are no moving parts.

2.1.1 COS and CTCSS inputs

Each port has a COS and CTCSS input to convey channel activity information to the FF- 800 operating system. The active voltage level can be user defined separately for each port -- this active level can be high, or low. High active levels are any input voltage above 3.0 volts (40 volts maximum) or floating (a disconnected COS input will go high due to a 10K pull-up resistor on each input) -- low active levels are any voltage below 0.8 volts (see the installation section for more detailed information on interfacing the FF-800). In addition to setting the active voltage level, there are several combinations of COS and CTCSS inputs that can be selected to signify channel activity. The following list describes each mode:

ModeConditions required for active status
COS onlyOnly COS active (CTCSS ignored)
CTCSS onlyOnly CTCSS active (COS ignored)
not CTCSSCOS active AND CTCSS inactive
COS & CTCSSCOS active AND CTCSS active
COS or CTCSSCOS active or CTCSS active
The user may select any of these options depending on the type of CTCSS solution that is desired for their RF system. These parameters (as with all configuration parameters on the FF-800) can also be changed as desired to reflect changing system requirements, or to allow for different operating modes for different situations.

2.1.2 PTT outputs

Each of the PTT and Logic outputs on the FF-800 consist of an open drain, high current MOSFET transistor. Each output can sink as much as 500 milliamps of current with a maximum on resistance of 0.2 ohms. The active (on) state of the logic outputs is user programmable. For PTT systems that require high active PTT signals that can source current (ie., a transmitter strip that keys by applying 13.8 volts to the power input) the user should refer to figure 3.7.4 for an example of driving an active high PTT transmitter.

2.1.3 Voter logic inputs

There are 8 logic inputs that are dedicated to receiving current voted receiver information from a multi-site voter. This information is used by the FF-800 to select the courtesy tone for the port assigned as a voted port. This selection can either be by last active COS, or most active COS. The voter logic signals expected by the FF-800 are one-of-N type (N = 1 to 8) where N = number of receivers in the voter. This means that the voter must provide a signal for each receiver and only activate the signal corresponding to the current voted receiver. The active level of each voter logic input can be individually set by the user for active high, or active low.

2.2 DTMF Command System

Standard DTMF signaling is used by the FF-800 to input function codes and data. The electrical specifications are given in the installation section; however, there are some timing considerations and configuration options that the user must know. The minimum valid duration of a DTMF digit is about 60 milliseconds, digits that are shorter than this will not be reliably accepted (if at all). In addition, the inter-digit delay (the time BETWEEN digits) must not exceed 4 seconds or the entry in progress will be aborted. There is also a function execute limit of 9 seconds from the last DTMF code -- if this time is exceeded, the command will not execute. Function execution begins when the input channel becomes inactive (ie., it loses COS). However, function execution can be forced to occur befo("he channel goes inactive by entering what is called the delimiter sequence. The delimiter sequence consists of the two DTMF digits "#*". Whenever this sequence is encountered, the FF-800 will immeadiately try to execute any DTMF codes that are pending in the buffer. The delimiter sequence is valid from any input source that accepts DTMF codes and can be used at any time.

DTMF codes are accepted from enabled Main or Link ports, or from the auxiliary DTMF input. If more than one port is active at a time, the DTMF decoder monitors the highest priority port. If function access is desired from a Remote base port, the receive audio from that port can also be connected to the auxiliary DTMF input to allow limited function access (RESET, PORT CONTROL, or any bank 4 MACRO). If a link must have reverse access, it may also connect to the auxiliary DTMF input to allow port activation from the link side when the link is turned off. If multiple inputs are to be connected to auxiliary DTMF, an external priority switch should be used to prevent collisions. The AUX DTMF input behaves somewhat differently from the normal input. The normal input requires COS to allow recognition of DTMF digits -- however, the AUX DTMF input does not require COS and does not require the delimiter sequence. This is because the recognition of tones is based on their entry timing. The same minimum validate time and inter-digit delay that is in effect for the normal input also applies to the AUX DTMF input. However, when the inter-digit delay expires for the AUX DTMF input, the FF-800 attempts to execute the contents of the auxiliary buffer. Thus, any commands entered via the AUX DTMF input will execute four seconds after the last digit is entered.

The FF-800 is designed to mute DTMF codes from the output of the repeater as soon as they are detected. The muted tone is replaced by a "cover tone" generated by the FF-800. However, the user can control the cover tone and muting with the following four modes:

ModeDescription
IndividualDTMF muting on, one cover beep for each DTMF detected
SteadyDTMF muting on, one cover beep every second
NoneDTMF muting on, no cover beeps
No muteDTMF muting off, no cover beeps

2.2.1 Control Receiver input

The control receiver input is a dedicated input for accepting DTMF digits. When control COS input goes active, any DTMF entry in progress on any other input (including control autopatch) is aborted and the DTMF decoder is switched to the control receiver. This input is isolated from the normal audio chain, such that audio on this input can not be passed to the repeater output. Also, there are no cover tones for a DTMF entry from the control receiver. When executing commands from the control receiver, the response will appear at any enabled main port (if the repeater is idle, the main port(s) will go to transmit to issue the function response and then go inactive after the response is complete).

2.2.2 Control Auto Patch input

The user may enable or disable the control autopatch for the FF-800 controller. The control autopatch allows the user to enter control functions from any DTMF equipped phone. When a control autopatch is in progress, DTMF entry from all receiver inputs (except the control receiver) is disabled, and the FF-800 will not mute any DTMF digits from these inputs. Command responses are routed away from the normal mixer input which means that the user on the phone will hear the FF-800's responses, but these responses will not appear at the repeater output. There is an activity timer that governs the access to the control autopatch, if no valid control or configuration commands are entered for 15 minutes (the default time -- the user may change this timer if desired), the FF-800 will hang-up the control autopatch and return the repeater to normal operation. If a control autopatch is inadvertently terminated without logging off, the only way to regain control (other than waiting for the time-out) is via the control receiver input, or the auxiliary DTMF input.

2.2.3 Auxilary DTMF input

The auxiliary DTMF decoder is provided to allow a second and independent control path for the FF-800. It is primarily intended for reverse access from links or remote bases, but can serve as a secondary control input if desired. The important difference between the control receiver and the auxiliary DTMF input is that there is no COS input for the auxiliary DTMF input. All digit entries are timed and execution occurs automatically four seconds after the last digit is entered. In restricted mode, only port control commands, reset, and bank 4 macros are recognized from the auxiliary input. In the secondary control mode, any valid command is recognized.

2.2.4 Main and Link Channel input

The FF-800 only responds to DTMF input from ports designated as "main" or "link". DTMF inputs are only recognized for the highest priority active COS that is applied to the FF-800. Lower priority inputs, or inputs which do not qualify for active status (ie., the port is off or the CTCSS inputs are not active as programmed) will not be recognized for DTMF input. "Link" or "main" ports that require DTMF access under any active status conditions should make use of the auxiliary DTMF input (see above).

2.3 Serial Port Interface Command System

The serial port interface firmware allows the user to connect a PC or terminal to the FF-800 to ease the programming and maintenance of the FF-800 system. The connection may be direct, via modem, or via packet TNC. There are several commands and functions that allow the FF-800 to control a modem or TNC that provide a variety of secure access methods. The baud rate is user selectable over a wide range to accommodate most standard modem or TNC protocols.

2.4 Speech Synthesizer

The speech synthesizer is a commercial quality device that uses Linear Predictive Coding (LPC) to produce speech. LPC is a method of compacting speech data that is very faithful at retaining the natural tone of the original speech. As such, the speech produced is of very good quality and is easily understood.

2.5 Telephone Interface

The FF-800 telephone interface is designed to connect directly to commercial phone lines and provides two additional signal connections that are optically isolated for protection. The "off hook" output is used to alert other systems on the same phone line that the phone is busy. The converse to this signal is the "busy input". This input can be driven by other systems to tell the FF-800 that the phone line is busy. If the busy signal is activated, the FF-800 will not allow autopatch traffic to occur.

2.6 Serial Peripheral Expansion Bus

The FF-800 provides a synchronous serial expansion bus that can be used for many enhancements to the user's system. Provisions for BCD frequency output allow the user to implement "frequency agile" remote bases -- plus, the expansion bus also communicates with FF Systems enhancement interfaces which allow the addition of Digital Voice Recorder, ICOM IC-901/900 radio interface, HF radio interface, as well as future interface designs.

2.7 Logic Outputs

There are eight user outputs that may be used as control signals for external systems. The serial peripheral expansion bus allows the user to expand the outputs by adding eight external outputs. This requires that the user provide a shift register I.C. to capture the serial data stream that contains the external output information (see appendix A for more information).

2.8 Logic Inputs

There are four logic inputs that can be used to trigger a user selected macro. For each input, a trigger can occur at the rising edge of the input, and another can occur at the falling edge. Such inputs are useful for setting up such features as a site intrusion alert or for signaling commercial power failures.

2.9 Analog Inputs

The FF-800 has four analog inputs which allow the user to sample various parameters (temperature, humidity, voltage, power, etc...) and report the telemetry on command. A standard LM335 temperature sensor IC can directly connected to the FF-800 to form the heart of a simple temperature sensor input. The analog inputs expect a voltage between 0 and 5 volts -- all inputs must be converted to this range before connecting to the FF-800. The user can then set up the input for a given conversion factor and units or use the standard telemetry commands for temperature or S meter readings.

2.10 Automatic Command Execution

There are several methods that the system operator may employ to engage automatic command. The macro system forms the basis of this ability by allowing a series of commands to be grouped into one. These commands may then be available for direct application by users, or they may be assigned to scheduler events, command trigger inputs, or the LTiZ detect feature (LTiZ is the FF Systems designation of the long tone interrupt zero standard for accessing emergency services -- the ARRL designation is LiTZ). The scheduler is very flexible and allows the operator to specify event times with "wild cards" -- these "wild cards" can indicate that events are to occur every year, month, day, day of week, hour, or minute.


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