Its center frequency is set on a trio of rotary switches and can range from 50 Hz to 990 kHz. Minimum resolution bandwidth is 10 Hz. It has a 1 MΩ input resistance.
Type 1L5 was sold from 1967 until the end of the classic plug-in scope line. Not particularly accurate in either frequency, bandwidth, or amplitude, it was no match for HP's 141T/8556A/8552B combination in performance, but it was a small fraction of the price.
Although Type 1L5 can operate in any 500-series scope*, it is most useful by far in the Type 549 storage mainframe which allows slow sweeps needed to match the narrower resolution bandwidths.
In conjunction with the 015-0107-00 "Swept Frequency Generator" (tracking generator), the 1L5 can also measure frequency response.