This post explains for the transistor D2499.
The Part Number is 2SD2499.
The function of this semiconductor is 1500V, NPN Transistor.
Manufacturers : Wing Shing Computer
High voltage, high-speed switching npn transistors in a plastic envelope with integrated efficiency diode,primarily for use in horizontal deflection circuites of colour television receivers [ … ]
Absolute maximum ratings ( Ta=25°C )
1. Collector-emitter voltage peak value (VBE = 0V) : VCESM = 1500 V
2. Collector-emitter voltage (open base) : VCEO = 600 V
3. Collector current (DC) : IC = 5 A
4. Collector current peak value : ICM = 10 A
5. Base current (DC) : IB = 2 A
6. Total power dissipation : Ptot = 50 W
7. Storage temperature : Tstg = -55 ~ 150 ºC
8. Junction temperature : Tj = 150 ºC