Head on generator.
HOG WAP-7 that GZB holds are mainly for Kalka Shatabdi.
WAP-5/7 were not given to GZB from the time BRC started getting WAP-5 but now again GZB got WAP-7. All those recent WAP-7 allotments to GZB are reported to be HOG.
HOG as in the engine itself generates electricity for the rake.