Purpose Of Relays - IBM 727 Manual Of Instruction

R l, 18, Run (09.04)
1AU, 1BU (10.01)
1AL (09.06)
1BL (09.04)
18-2 (09.01)
18-3,4 (09.03)
R2, Load rewind
(09.04)
2AU (09.04)
2AL (09.04)
2BU (09.06)
2BL (09.05)
R3, R31, Load rewind
(09.05)
3AU (09.01)
3AL (09.04)
3BU (09.06)
3BL (09.06)
31-2 (09.01)
20. 0

PURPOSE OF RELAYS

They are always picked except when unloaded. When dropped,
they indicate a failure in one of the machine interlocks, such
as a blown fuse, tape breakage, or DC power failure.
When down, they allow full brake to both stop clutches.
It controls phases 1 and 2 AC power.
In case of an interlock failure, drop R4 if it was up, so the
1AU and 1BU pts. can brake both reels.
In case of an interlock failure during low-speed rewind, stop
tape by dropping the manual start line.
Insure that the interlock conditions are satisfied before
allowing the ready line to be raised, or the ready light to be
turned on.
It is picked when the load rewind button is pressed. If this
occurs in an unload status or in the high-speed area, R2
holds until both capstans are extended. If load rewind button
is pressed when loaded in the slow-speed area, R2 is picked
until the button is released.
P ickR 5, 6, HD7 while rewinding when or if the reel arm switch
is closed, or when the reset key is pressed while rewinding in
the high-speed area.
It is the hold point for R2.
When initiating a rewind in the slow-speed area, it prevents
a short pick to HD8 when R2 drops.
the load rewind button is released, if using manual control.)
Pick R3, 31. Trip R21, 26, if latched.
Same as R2
It shunts the load point and tape end lights during load re ­
wind until the capstans extend.
light brighter during the time it might be used. It also pre­
vents the en d-of-file mark from causing a false tape break
indication.
It allows the run relays to hold during load rewind when tape
is not in the columns. It also prevents dropping the run r e ­
lays if the tape break light burns out during a high-speed
rewind. Dropping the run relays would put full brake on
both reels.
Pick R13 during load rewind until the capstans are out.
(See R13.)
When a rewind in the slow-speed area is initiated, it pre­
vents a short pick to HD8 when R2 picks.
when the load rewind button is pressed, if using manual
co n tro l.)
Prevent getting a reverse start during load rewind until both
capstans are extended.
85
(This would occur when
This makes the tape break
(This would occur