<![CDATA[Indonesian vocational high school (Sekolah Menengah Kejuruan, SMK) students must master unshielded twisted pair (UTP) cabling, yet pin order, cable types, and connector logic are difficult to visualize, practice time is short, and equipment is often scarce. Grounded in the cognitive theory of multimedia learning and cognitive load theory, this study designed an Android-based virtual laboratory that uses isometric (pseudo-3D) visualization to make the cabling workbench visible on ordinary smartphones. The study addresses a gap in mobile and simulation-based vocational learning research, which has focused on logical network configuration in higher education and has rarely addressed physical cabling at the secondary level. It examined the product's validity, practicality, and preliminary effectiveness as a supplementary medium for UTP cabling concepts. Development followed the 4-D model (define, design, develop, disseminate). Three media and three material experts evaluated the prototype using Aiken's V, and three practitioners and 16 Grade 10 Software and Game Development (PPLG) students rated its practicality. Effectiveness was examined in a pilot study using a pre-experimental one-group pretest–posttest design over eight sessions with a 24-item conceptual test (KR-20 = 0.94). The sample was the entire Grade 10 PPLG class (total sampling); an a priori power analysis showed that 15 participants were needed to detect a large paired effect (dz = 0.80, α = .05, power = .80). Media and material validity were 0.84 and 0.91. Practicality averaged 88.00% (practitioners) and 85.25% (students). Mean scores rose from 62.50 (SD = 12.73) to 85.68 (SD = 8.47), t(15) = 8.14, p < .001, dz = 2.04, ⟨g⟩ = 0.62, and 93.75% of students reached the mastery level. Because no control group was used, this gain indicates an association with the intervention rather than a causal effect, and it may also reflect regular instruction, testing, and maturation. The isometric virtual laboratory is a valid and practical supplementary medium for resource-limited workshops, and controlled studies are needed to establish its effectiveness.]]>
