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Testing Permissive Make Relays

Goal of this page - Discuss "Testing Permissive Make Relays",
as used in the 1401 system, especially the 1402

This is what we are talking about ;-)) - from IBM-FU-05-Commutation Control - Permissive Make Relays
Permissive Make Relays

     The trend to higher speed machines has created the need for a high speed multi-contact relay with constant tension and no contact bounce. The permissive make relay was developed to meet this need. It will operate in about half the time of a wire contact relay and with contact bounce practically eliminated.
      This relay is made in 4, 6, and 12 position sized, and will add color identification to relay gates. the 4 position relay base is red, the 6 position is green, and the 12 position is blue.
      The permissive make relay gets its name as the contact being closed is permitted to make by the action of the armature. Each contact position has two two sets of wire contact. One set of contacts is held open by the relay armature while the other set is permitted to make with the contact tension being dependent only on the contact wires. When the armature is attracted, the N/C contact wires are pushed away from the common contact and the wires that had been held open are dropped lightly on the common contact without bounce or oscillation. The contact tension is independent of armature travel.

From Stan Paddock < STPaddock @ sbcglobal . net >

Permissive Relay Tester:

  1. The gap between a wire and the contact bar is very close.
  2. The armature does not push any contacts closed, the armature gets out of the way and let the spring of the wire make the contact.
    No contact bounce.
  3. Hence the name, the relay 'permits' the wire to make contact.
Stan Paddock brought in his Permissive Relay Tester he just completed. More information on it may be found at This box along with a laptop can test a GREEN (6 section) or a RED (4 section) relay in under 2 seconds.
(Local Copy)

You can see this happen at:

Posted Dec 12. 2015