Space code selector supervisory system

DURING the past 20 years, there have been numerous supervisory systems using various designs and basic principles of transmitting signals such as tone, counting chain codes, or sequence chain codes. Any supervisory system should fulfill the following essential operating requirements: 1. Transmit control circuit selection code and check this transmission before the control operation is performed. Prevent the operation if the correct checking signal is not received. 2. Be suitable for operation over any commonly available type of channel for use in controlling a number of outlying stations from a single control station. 3. Components should harmonize with other switchboard devices and thus be suitable for building into standard switchboards. 4. Equipment should be easy to expand to take care of future growth. Be simple, easy to install, maintain, test, and operate. Be rapid, have uniform speed of operation for all points. 5. Be available for either 48-volt or 125-volt d-c operation and have the same standard range of battery voltage as the remainder of the switchgear devices. 6. Include provision for telemetering and telephone communication.