Salyut 1-type Soyuz 7K-T/A9 for 3 cosmonauts without space suits. This was the Original Soyuz 7K-OK upgraded for the military Almaz space stations. The probe and drogue docking system (left) permitted internal transfer of cosmonauts from the Soyuz to the station.
The second generation of the Soyuz spacecraft, the Soyuz Ferry or Soyuz 7K-T, comprised Soyuz 12 through Soyuz 40 (1973-1981). In the wake of the Soyuz 11 tragedy, the spacecraft was redesigned to accommodate two cosmonauts who would wear pressure suits at all times during launch, docking, undocking, and reentry. The place of the third cosmonaut was taken by extra life-support systems. Finally, the 7K-T, being intended purely as a space station ferry, had no solar panels, instead sporting two large whip antennas in their place. As a result, it relied on batteries which only provided enough power for two days of standalone flight. The idea was that the Soyuz would recharge while docked with a Salyut space station, but in the event of a docking or other mission failure (which ended up happening on several occasions), the crew was forced to power off everything except communications and life support systems until they could reenter.
In addition, the standalone flights of Soyuz 13, Soyuz 16, Soyuz 19, and Soyuz 22 used a variant of the 7K-T with solar panels, and in the case of 13 and 22, special camera apparatus in place of the docking mechanism. A large Orion 2 astrophysical camera for imaging the sky and Earth were used on the former and an MKF-6 Zeiss camera on the latter.
Another modification was the Soyuz 7K-T/A9 used for the flights to the military Almaz space station. This featured the ability to remote control the space station and a new parachute system and other still classified and unknown changes.