IB-39588-a.pdf
Temporary Correction T-1 to instruction Book for Radio Receiving Sets
AN/FRR-21,AN/FRR-22, AN/FRR-23, NAVSHIPS 92211
Describes engineering updates for unit bearing serial number 26 and up.
Includes schematics and system assembly drawings

IB-39588-b.pdf
Temporary Correction T-2 to instruction Book for Radio Receiving Sets
AN/FRR-21,AN/FRR-22, AN/FRR-23, NAVSHIPS 92211
Describes engineering changes for
AN/FRR-21 serial numbers 107-220 inclusive, 335 and up
AN/FRR-22 serial numbers 236 and up
AN/FRR-23 serial numbers 342-492 inclusive, 643 and up
Replacement of 5647 tube diodes with 1N458 semiconductor diodes

Compliments of Virgil Cheng, vr2xgm.