An aircraft cabin blower system (100; 200; 300) comprising: a cabin blower compressor (102; 202; 302); a first transmission (110; 210; 310) having a transmission output mechanically coupled to the cabin blower compressor and first (119; 219; 319) and second (120; 220; 320) transmission inputs; and an electrical circuit comprising a first (118; 218; 318) and second (122; 222; 322) electrical machines and a power management system (124; 224; 324), and wherein, in a blower mode of the system: (i) the first transmission is configured to receive mechanical power at the first transmission input from a first part of a gas turbine engine; (ii) the first electrical machine (118; 218; 318) is configured to receive mechanical power from a second part of the gas turbine engine and to act as a generator to provide electrical power to the power management system (124; 224; 324); (iii) the second electrical machine (122; 222; 322) is configured to act as a motor and to provide mechanical power to the first transmission (110; 210; 310) at the second transmission input (120; 220; 320); (iv) the second electrical machine (122; 222; 322) is configured to be driven by electrical power from the power management system (124; 224; 324); and (v) the transmission output is configured to drive the cabin blower compressor. a cabin blower compressor (102; 202; 302); a first transmission (110; 210; 310) having a transmission output mechanically coupled to the cabin blower compressor and first (119; 219; 319) and second (120; 220; 320) transmission inputs; and an electrical circuit comprising a first (118; 218; 318) and second (122; 222; 322) electrical machines and a power management system (124; 224; 324), and wherein, in a blower mode of the system: (i) the first transmission is configured to receive mechanical power at the first transmission input from a first part of a gas turbine engine; (ii) the first electrical machine (118; 218; 318) is configured to receive mechanical power from a second part of the gas turbine engine and to act as a generator to provide electrical power to the power management system (124; 224; 324); (iii) the second electrical machine (122; 222; 322) is configured to act as a motor and to provide mechanical power to the first transmission (110; 210; 310) at the second transmission input (120; 220; 320); (iv) the second electrical machine (122; 222; 322) is configured to be driven by electrical power from the power management system (124; 224; 324); and (v) the transmission output is configured to drive the cabin blower compressor. (i) the first transmission is configured to receive mechanical power at the first transmission input from a first part of a gas turbine engine; (ii) the first electrical machine (118; 218; 318) is configured to receive mechanical power from a second part of the gas turbine engine and to act as a generator to provide electrical power to the power management system (124; 224; 324); (iii) the second electrical machine (122; 222; 322) is configured to act as a motor and to provide mechanical power to the first transmission (110; 210; 310) at the second transmission input (120; 220; 320); (iv) the second electrical machine (122; 222; 322) is configured to be driven by electrical power from the power management system (124; 224; 324); and (v) the transmission output is configured to drive the cabin blower compressor.