Streckeisen describes three redesigns of their electronics that resulted in differing transfer functions above 10 Hz. Approximate times and serial numbers when new electronics were implemented are shown here, though older sensors that have had their electronics replaced may have newer generation electronics.
| Generation | Month/Year | Serial # ((M)MYYxx) |
| 1 | 01/90 to 09/94 | 19001 to 99442 |
| 2 | 09/94 to 04/97 | 99443 to 497xx |
| 3 | 09/97 to present | 997xx and later |
This document from Streckeisen has more:
Detailed list of STS-2 Generations.
| Manufacturer | Model | Period / Frequency | Sensitivity | RESP Filename | Source | Comments |
| Streckeisen | STS-2, generation 1 electronics | 120 s / 0.00833 Hz | 1500 V/M/S | RESP.XX.NS081..BHZ.STS2_gen1.120.1500 | Streckeisen | PASSCAL |
| Streckeisen | STS-2, generation 1 electronics | 120 s / 0.00833 Hz | 20000 V/M/S | RESP.XX.NS082..BHZ.STS2_gen1.120.20000 | Streckeisen | |
| Streckeisen | STS-2, generation 2 electronics | 120 s / 0.00833 Hz | 1500 V/M/S | RESP.XX.NS083..BHZ.STS2_gen2.120.1500 | Streckeisen | PASSCAL |
| Streckeisen | STS-2, generation 2 electronics | 120 s / 0.00833 Hz | 20000 V/M/S | RESP.XX.NS084..BHZ.STS2_gen2.120.20000 | Streckeisen | |
| Streckeisen | STS-2, generation 3 electronics | 120 s / 0.00833 Hz | 1500 V/M/S | RESP.XX.NS085..BHZ.STS2_gen3.120.1500 | Streckeisen | USArray/TA/BB/FA, PASSCAL |
| Streckeisen | STS-2, generation 3 electronics | 120 s / 0.00833 Hz | 20000 V/M/S | RESP.XX.NS086..BHZ.STS2_gen3.120.20000 | Streckeisen | USArray/BB |
Mary Templeton 10/29/2014