Reverting to what early Ottoman Naqshbandis made of the rabita, we may begin with the following description by Mustafa al-Sadiqi (R).

Rabita requires that the practitioner attach himself in obedient service (khidma) to a shaykh who has reached [the station of witnessing], and that he keep the shaykh’s company (suhba) continually, fill himself with utmost attentiveness to him, cement his love for him in his heart, and [learn to] preserve the shaykh’s visual form (sura) in his imagination. Thus is generated between them such a bond and union that the emancipation of divine energy (fayd) reaching the shaykh can pour forth to the disciple without a need for a great deal of ascetic exercises (mujahada wa ijtihad). When the rabita occurs and [the practitioner] feels its effect in his heart, he should strive to preserve it. Whenever there is slackening of that [effect] he should return to companionship with the shaykh, time after time, until the effect returns to him and becomes a natural disposition (malaka).

ref: Le Gall, Dina (2005). A Culture of Sufism: Naqshbandi’s in the Ottoman World, 1450-1700 (pg 113) New York: State University of New York Press.