Instrument Description The TM 515 is a five-wide power module compatible with most TM 500 plug-ins. It provides unregulated ac and dc supplies and nondedicated power transistors for use by the plug-ins. This mainframe does not have a high-power compartment but does feature forced-air cooling. Available options allow the rear interface to be customized (Option 5), operation from power sources with a line frequency of up to 400 Hz (Option 6), and specific interconnections for specialized plug-ins (Option 7).