Mu njira yotumizira mauthenga a digito, pali mitundu iwiri ya transceiver ya digito, imodzi imatchedwa "Plesiochronous Digital Hierarchy" (Plesiochronous Digital Hierarchy), yotchedwa PDH optical transceiver; ina imatchedwa "Synchronous Digital Hierarchy" (Synchronous Digital Hierarchy), yotchedwa SDH optical transceiver.

Dongosolo logwiritsa ntchito plesiochronous digito series (PDH) ndikuyika wotchi yolondola kwambiri pa node iliyonse ya netiweki yolumikizirana ya digito, zizindikiro za mawotchiwa onse ali ndi mlingo wofanana. Ngakhale kuti wotchi iliyonse imakhala yolondola kwambiri, nthawi zonse pamakhala kusiyana pang'ono. Pofuna kuwonetsetsa kuti kulumikizana kuli bwino, kusiyana pakati pa mawotchiwa sayenera kupitirira malire omwe atchulidwa. Chifukwa chake, njira yolumikizira iyi siyolumikizana kwenikweni, chifukwa chake imatchedwa "quasi-synchronous."

M'mbuyomu ma telecommunication networks, zida zambiri za PDH optical transceiver zidagwiritsidwa ntchito, mndandandawu umakhala wosinthika bwino pakulankhulana kwachikhalidwe. , ndipo mauthenga ambiri a digito amayenera kusamutsidwa, choncho, mndandanda wa PDH sungathe kukwaniritsa zofunikira za chitukuko chamakono cha telecommunication ndi kayendetsedwe kamakono ka telecommunication network. SDH ndi njira yotumizira yomwe yatulukira kuti ikwaniritse zosowa zatsopanozi.