The ComNet FDC8ISOT 8-Channel Contact Closure Transmitter unit provides up to eight independent normally-open (NO) dry contact closures over one multimode or single-mode optical fiber, when used in conjunction with the companion ComNet model FDC8NLR Non-Latching Receiver or FDC8R Latching Receiver units. Each of the contact closure inputs are optically isolated at 1500V to ground, for those applications where high stray or transient voltages may exist. Microprocessor-based logic in the FDC8ISOT Transmitter detects a customer-furnished switch or contact closure, and encodes the closure into robust data packets that are mapped and transmitted to the FDC8NLR Receiver. Packets received with excessive bit errors will not result in random changes in the receiver relay contact resting or actuated states, making this system ideal for mission-critical remote switching applications. Plug-and-play design ensures ease of installation and operation, and no optical or electrical adjustments are ever required.