TNC3S High-Speed dual port Packet-Controller

User manual (hardware)  download (500 kB)

Software-manual download (400 kB)

Short list of technical specifications

Prices, how to order

Since 1993, SYMEK produces a unique High-Speed-Controller for Packet-Radio.

The TNC3S is the top Packet Radio-Controller for Amateur-Radio.

Two modems may be run simultaneously. The Modems are plugged-in and can be combined with the base model as desired.

Ideal to use it as a network node with the X-Net Software.

Data communication with extreme high speed is possible. Limit over 1 MBit/s AX.25 speed.

Software: Turbo-Firmware for 10 to max. 200 logical radio channels, Mailbox for 10 User logged in at the same time, Crossdigipeating, KISS, SMACK, test program, DAMA. Compatible to most of the common terminal-programs as GP, SP, AHP, TOP, VP etc.. Download of TNC3-Programs from diskette into the CMOS-RAM or into Flash-EPROM (Option) possible. May be used as TheNetNode (=Net-ROM), FlexNet and TCP/IP node. Your own C-programs may run on the TNC3. The TNC3 ist 100% plug-compatible to the former TNC2 as TNC2S, TNC21S or TNC2H.

The TNC3S is used by far more than 1000 Radio-Amateurs worldwide. It may be connected to every Computer with a RS232 interface. The includes disc contains programs for PC and Atari.

Description of TNC3S

Two Modems

In the TNC3, there is space for two Modems, e.g. a 1200 Baud AFSK modem and a 9600 Baud FSK modem. Both modems are acessed simultaneously by the TNC3-Controller: You can read the received data of both modems on the screen. Connects may be started either on modem #1 or modem #2. The modem ports may be distinguished by the port-number, which is added to the callsigns as a prefix as e.g. 2:DB0ID.

Alternatively, each of the logical channels can be assigned to one of the modemports. Select the channel and define the modem with the command #PORT 1 or #PORT 2.

If the RS232 port is not required (e.g. when the TNC3 is to be used as remote digipeater), a third modem may be attached. The connector for a third modem can be added but if the two modem slots are occupied, the third modem has to be mounted externally.

16 Bit Processor

Heart of the TNC3 is a powerful 16/32 Bit mikroprocessor of Motorola MC68000 family. The data bus to EPROM and RAM is 16 Bit wide, this makes a fast data transfer possible. The CPU runs with 15 MHz clock. The processor has a built-in RISC-based communications controller which transfers complete AX.25 packets directly to the RAM without intervention of the CPU. This makes the TNC3S about 100 times faster as the TNC2, where every byte caused a interrupt and had to be transferred individually to the RAM.

The 24 Bit wide address-bus makes it possible to address far more memory as with the Z80-based TNC2.

AX.25 Speed

the CPU is able to process serial data on three channels simultaneously. The peak baudrate is 1.6 MBaud per channel fullduplex, but the total data should not exceed this limit. As  the RS232 is normally limited to 115 kBaud, you may run the TNC3 for example with both ports at 614 kBaud fullduplex without problems.

Selectable Software

The TNC3-EPROM contains several different programs, which may be selected by a DIL-Switch on the rear side of the TNC3. Available today are Turbo-Firmware, System and Modem-test-program, TNC3-Mailbox (Mailbox+Firmware, english and german), KISS/SMACK, TNC3-operating system, Hayes-mode-Firmware.


For 1200 Baud AFSK and 9600 Baud FSK (G3RUH), standard modems are available. For special applications, we can deliver FSK-modems up to 614 kBaud.
The TNC3 has two modem-slots. The size of the modems is 80x120 mm, the modems are fixed with screws and connected with a ribbon cable.
The transmit clock is generated by the modem and may be varied from nearly zero to up to 1 MHz.

RISC-Coprocessor for Data Transmission and Receiption

The TNC3-Processor contains three SCC's (Serial Communications Controller) which encode or decode the AX.25 packets without intervention of the CPU. The received data packets are stored via 6 DMA channels directly in RAM. This makes it possible to receive serial data packets with speeds up to 1,6 MBaud (1 600 000 Baud). Data is processed packet-wise instead of byte-wise (TNC2). The processing of the data packets is done by the RISC coprocessor, which was designed to do this tast with optimal per-formance.

Large Memory Space for RAM and ROM

The CMOS-RAM of TNC3 is batteriy-buffered and keeps all data even when the TNC power is off. The standard memory has 64 kByte and may be extended to up to 2 Mbyte by changeing the RAM chips. We recommend to use 256 kByte.

The program of TNC3 is stored in a pair of 27C1000 EPROMs. Larger EPROMs or Flash-EPROMs may be used as well.

TNC3-Operating System

The TNC3 Software is based upon the TNC3 Operating System, which controls the different application programs as Turbo-Firmware, Mailbox etc. The operating system may be accessed directly by a attached terminal, some commands (mostly file system commands as ll, more, copy, start a application...) are available. The CMOS-RAM acts like a disc-drive "R:", which can be accessed by the supplied terminal program in the same way as the other drives (A:, C:, D: ...) of the computer. The CMOS RAM is battery buffered, all data is retained at power-off.

Upload and download

Data can be copied between PC and TNC3 via the RS232 interface. TNC3-data (text files, mails etc.) can be backed-up on a PC disc, program-files, updates etc. may be transferred from PC to the TNC3 ramdisc. The RS232 speed is up to 115 kBaud, when a Flash-EPROM is installed in TNC3S, new programs may be programmed directly from the PC to the TNC3 Flash-EPROM.

Fast RS232 Interface

The RS232 baudrate can be selected with three switches at the rear of the TNC3: 1200, 2400, 4800, 9600, 19200, 38400, 57k6 and 115k2 Baud are available.

Autostart Select

As there may be different application programs stored in the TNC3 ROM, you can define a 'autostart' program, which is executed at power-on. With 5 switches at the rear of TNC3, you can select one of 32 possible autostart-files. DIP 0 starts the operating-system, DIP1 the turbo-firmware, DIP 8 the KISS-mode, DIP 9 the mailbox and DIP 6 the system test program.


A piezo-beeper sounds, when data packets are received, when a connect is executed or when a mail for the sysop arrived. The sound can be switched on and off with commands.

Selective Digipeating / Connect

Normally, a digipeater (TNC) may be used by everybody. If this function is to be restricted, you may define a list of stations, who must NOT use the TNC3 as digipeater. Alternatively, you may set up a list of calls, which are exclusively allowed to use the digipeater. Users of the TNC3 mailbox may execute the CON command and connect other stations from there. This function may be restricted in the same way as the digipeating.

Manuals, Documentation

The TNC3S comes with a comprehensive and complete manual. Select German, French or English language. The schematic and hardware description is included.

Real Time Clock

The TNC3S includes a battery operated real time clock (RTC), the system timer is running even when power is off.


The Turbo-Firmware of TNC3S supports the Nord><Link DAMA mode. If the TNC3 is to be used in nets without DAMA access control, this has no effect.


New versions of the TNC3 Software may be installed by changeing the EPROMs or by reprogramming the Flash-EPROMs. Updates for Flash-EPROMs are available via some amateur-radio mailboxes.


The TNC3 includes SMACK, a compatible enhanced KISS-Mode. With special PC-programs (NOS, WNOC, WAMPES etc.), data packets up to 2 kByte are generated in PC and transmitted by the TNC without changes. Useful for TCP/IP protocol and special applications.

Hayes-Mode (AT-Commands)

The TNC3 software include a Hayes-compatible mode, i.e. the TNC3 uses the same commands as a usual telephon modem. This is advantaegeous if a dialled telephone link is to be replaced by a packet-radio connection. The Connect is established by the AT DT call command and disconnected with +++ AT H. 'via' traffic via a digipeater is possible. While connected, the link is fully transparent, packets are sent after a delay (e.g. 1 s) or whenever the packet length is exceeded. The RS232 format can be set to 7 or 8 Bit, e/o/n parity and baudrates between 1200 to 115200 Baud. Hardware handshake is not provided.

SLIP mode for TCP/IP operation

If the SLIP (Serial Link Transfer Protocol) command is set, you can attach a TCP/IP server to the TNC3 or you can run the TNC by use of a Netscape PC-software. Future packet applications using Internet Protocol may be run without KISS or NOS drivers.


A reliable watchdog will restart the TNC3 CPU in case of software failure. But the TNC3 operating system is so stable, that the system will run hundreds of days without any reset.

Turbo-Firmware with Turbo-Hostmode

The firmware of TNC3S is compatible to the Hostmede, defined by WA8DED. Commands are entered with the escape character. For the dual port functions, some special commands have been added, like #PORT etc. The Turbo-Firmware supports up to 200 logical channels and is ideally suited for use with mailbox systems or packet-cluster.

TNC3 Mailbox Program

The programs TNC3BOX is identical to the standard Turbo-Firmware but offers a complete mailbox for the users. In normal hostmode-operation, multiconnect to 20 stations is possible. At the same time, the mailbox may be connected by up to 10 users simultaneously. The mail (up to 1.9 MByte) is stored in the battery backup RAM. At first login, a user file with date and name is stored. The box is organised in public and private (user-) boards. When passing a authorisation procedure, the sysop has access to some sysop-commands which allow creation and deletion of boards, transfer of data and program files into TNC3 RAM and starting of application programs. While being logged into the mailbox, it is possible to connect other stations by use of the CON command.

Remote Update

New programs or even the content of the EPROM may be transferred into the TNC3 RAM via the mailbox program, using the common BOXBIN protocol. With the FLASHDIG command (accessible to the sysop), you can copy this file into Flash-EPRON und thus do a complete update of the TNC3 via a radio link.

Intelligent Digipeating, Gateway, Connect

As the TNC3 has two radio ports, digipeating may work "in and out = same port", but also crossed "one port in, other port out" (Crossdigipeat mode). As the TNC3 keeps a long MH-list, it is also possible to let the TNC3 decide on which port the digipeated data will be output: The TNC3 'searches' the destination call in its MH-list and looks up, via which of the two ports this specific call had been head last. The user types CONNECT XYZ via TNC3DIGI and the TNC3 decides if the packets are to be digipeated on the same or the other port. No question, that the baudrate of the two ports may differ. so, the TNC3 can act as intelligent gateway between two frequencies or between two baudrates (e.g. 1200 / 9600 Baud). Similar to the intelligent digipeating acts the intelligent connect: When you execute a C <call> command, the TNC3 determines the port, where the station was heard last and tries to connect via this port.

X-Net Digipeater Software

There exists a software for TNC3, which can be used similar to Turbo-Firmware and TNC3BOX, but includes a real TheNet (=Net-ROM) plus FlexNet plus TCP/IP router! All three protocols are handled simultaneously, the TNC may act as 'normal' TNC with the mailbox as well. The Software can be downloaded from the internet page of swiss-artg and is free. For more information about this software try the pages of the swiss amateur radio teleprinter group. In Germany, there are experimental TNC3-systems running with 614 kBaud links between digipeaters and 153 kBaud user access. English language description of X-Net is found at

Case, Electromagnetic compatibility

The TNC3S is built up on a multilayer SMD board and has filters on all outgoing lines to reduce RF interference and -susceptibility.  


For TNC3, there are two modems available:
AFSK1200 for 1200 Baud AFSK (Bell 202) and FSK9601 (G3RUH-compatible modem) for 9600 Baud FSK. This modem can be easyly modified for other baudrates from 4800 up to 614k Baud.

The modems operate in the same way as the modems used with the TNC21 or TNC2H. The size is 80x120 mm, they can be plugged in the TNC3 with a 20 wire ribbon connector. Signals: TxD, RxD, DCD, PTT, TxC and RxC. The transmit clock is derived from the modem oscillator. The TNC3 accepts every baudrate from zero up to 1.6 MBaud.


The TNC31S is similar to the TNC3, it uses the identical software.

Here the main differences between TNC3S and TNC31:

The TNC31S has only space for ONE modem instead ot two.
The RAM of  TNC31S is 128 kByte, the TNC31SX has 512 kByte RAM.
The TNC31S has 128 kByte (TNC31SX: 512 kByte) Flash-EPROM for program storage.
The TNC31S has no battery buffered realtime clock (RTC) (but the TNC31SX has it)
The TNC31 is smaller: 104x42x125 mm aluminuim case similar to TNC3
The modems for TNC3 and TNC31 are the same: 1200 Baud up to 307 kBaud and more.
The power consumption of TNC31 is somewhat higher compared with TNC3
TNC31 is a very cost-effective solution for high-speed packet-radio