24-months Study to Evaluate Safety and Efficacy of Peroneal Transcutaneous NeuroModulation in Subjects With Parkinson's Disease and Essential Tremor

Inclusion Criteria: * Has completed participation in study TS004-PD * Competent and willing to provide written, informed consent to participate in the study. * Stable dose of any chronic medications, if applicable, for 30 days prior to study entry * Willing to comply with study protocol requirements. * Subject agrees not to participate in another study from 30 days prior the baseline visit until the final study visit. * For subjects with PD: * Bradykinesia in "on" period based on clinical assessment * Rigidity in "on" period based on clinical assessment * Hand/arm exhibiting tremor (resting and/or intentional and/or postural) ≥ grade 1 as assessed by the MDS-UPDRS tremor score in "on" period * For subjects with ET: * Visible hand/arm and/or foot/leg tremor (resting and/or intentional and/or postural) ≥ grade 1 as assessed by the TETRAS Exclusion Criteria: * Implanted electrical medical device, such as a pacemaker, defibrillator, or deep brain stimulator * Suspected or diagnosed epilepsy or other seizure disorder * Presence of clinical signs or diagnosis of dementia * Swollen, infected, inflamed areas, or skin eruptions, open wounds, or cancerous lesions of skin at stimulation site * Presence of clinical signs of peripheral neuropathy on lower limbs * Presence of chorea and/or dyskinesia * Clinical symptoms or diagnosis of major depressive disorder * Presence of any other neurodegenerative disease. These may include multisystem atrophy, progressive supranuclear palsy, dementia with Lewy bodies, and Alzheimer's disease. * Botulinum toxin injection within 6 months prior to study enrollment * Subject is breastfeeding, pregnant, intends to become pregnant during the study, or of childbearing potential, sexually active and not practicing a highly reliable method of birth control (these are methods with a failure quotient of \<1% year such as hormonal implants, injectable contraceptives, oral contraceptives of combination type, intra-uterine pessaries restricted to hormone contraceptive coil, sexual abstinence or vasectomy of the partner). The pregnancy test in urine at Visits 1 needs to be negative in women of childbearing potential. * Subjects unable to communicate effectively with the investigator and staff * Life expectancy less than 6 months * Subject with active malignant disease * Subject who, in the opinion of the physician, may interfere with optimal participation in the clinical trial or may pose a risk to the subject * Characteristics indicating a poor understanding of the study or characteristics that indicate the subject may have poor compliance with the study protocol