The Tektronix TR501 is a tracking generator plug-in for the TM500 system.
The TR501 can work with the 7L12.
The TR501 and TR502 are essentially the same instrument except for the output attenuators and logic interface added in the TR502.
- Tektronix TR501 @ barrytech.com
- TekScope Vol. 7 No. 5, 1975 p.11+: Fred Telewski, A high-stability 100 kHz to 1.8 GHz tracking generator
- TR501 repair @ Nederlands Transistorforum (Dutch) with photos