"The mortar package is activated by the "arm grenades" and "fire grenades" commands from Earth. The arm grenades command is applied to and gated through the command gating to the grenade arming circuitwhich charges the regulaz and sequential firing capacitors of the four grenades by applying a Z4-volt arming signal. A grenade arm pulse is also applied to the data handling function indicating receipt of the command."

Page 2-170 (179 of the PDF) of reference [1].

[0] https://ntrs.nasa.gov/search.jsp?R=19710014816 [1] https://ntrs.nasa.gov/api/citations/19710014816/downloads/19...