Agilent Technologies 1660A Series User Reference page 29

Probing
General-Purpose Probing System Description
Probe and Pod Grounding
Each pod is grounded by a long, black, pod ground lead. You can connect the
ground lead directly to a ground pin on your target system or use a grabber.
To connect the ground lead to grounded pins on your target system, you
must use 0.63-mm (0.025-in) square pins, or use round pins with a diameter
of 0.66 mm (0.026 in) to 0.84 mm (0.033 in). The pod ground lead must
always be used.
Each probe can be individually grounded with a short black extension lead
that connects to the probe tip socket. You can then use a grabber or the
grounded pins on your target system in the same way you connect the data
lines.
When probing signals with rise and fall times of ≤ 1 ns, grounding each probe
lead with the 2-inch ground lead is recommended. In addition, always use
the probe ground on a clock probe.
Probe Leads
The probe leads consists of one 12-inch, twisted-pair cable; one ground tap;
and one grabber. The probe lead, which connects to the target system, has
an integrated RC network with an input impedance of 100 kΩ in parallel with
approximately 8 pF, and all in series with 250 Ω. The probe lead has a
two-pin connector on one end that snaps into the probe housing.
Probe lead connector
Probe Ground Lead
2–6
Probe ground