​Brother typewriter and its modem

"​The typewriter often surprised us with its random writes, without us touching the keyboard. What to do? Repairing this electronics with on-board means is impossible. Finally, we knew where this phenomenon came from: the transmitter, poorly tuned to the antenna (standing wave ratio), radiated part of its power into the room, which disrupted the operation of the machine's processor. Even when cutting off his power supply, the fault persisted. It usually took a month to wait for the machine to be reusable. We then had the idea of discharging the machine of its static electricity by means of large sheets of aluminum foil and everything was back to normal."

Peter Kunz - HB9MCL  

Electronic typewriter with thermal printer - technical sheet:

• Thermal paper roll (beware of the sun)
• Small internal memory 14kB
• 25 character liquid crystal display
• RS232 interface
• 6Vdc power supply / 220Vac block

Pactor modem - technical sheet:

• Transforms the 8-bit serial data coming from the Brother machine into 2 different audio tones (zero and one logical) which will then be modulated and transmitted in SSB / AFSK
• Decodes the 2 tones on reception and sends them back to the Brother machine (printer)
• ARQ transmission mode, meaning with error correction, so the modem also manages the fast switching between RX and TX (max 20ms)
• Active error correction (FEC, Reed Salomon)
• With its processor, manages the direction of transmission (transition from transmission to reception and vice versa)
• 12Vdc power supply

Michel Vonlanthen - HB9AFO