Specifications are subject to change without notice (25.10.99) 1
Timers
Mono-function, plug-in, delay
on release, miniature time re-
lays up to 60 s covering 2
individual time ranges. These
economical timers are often
used to switch on an exhaust
fan and keep it running for a
certain period of time after
disconnection of power sup-
ply.
Plug Output Time ranges Supply: 24 VAC Supply: 120 VAC Supply: 220 VAC Supply: 24 VDC
Circular SPDT 0.15 - 6 s B 128 024 006 B 128 120 006 B 128 220 006 B 128 724 006
8 pins 1.5 - 60 s B 128 024 060 B 128 120 060 B 128 220 060 B 128 724 060
Circular SPDT 0.15 - 6 s B 121 024 006 B 121 120 006 B 121 220 006 B 121 724 006
11 pins 1.5 - 60 s B 121 024 060 B 121 120 060 B 121 220 060 B 121 724 060
Time ranges 0.15 - 6 s
1.5 - 60 s
Time range accuracy 0 to +20% on max.
min. actual time ≤min.
set time
Repeatability deviation ≤1%
Time variation
Within rated power supply ≤0.05%/V
and ambient temperature ≤0.2%/°C
Reset Power supply interruption
Time and/or relay ≥500 ms
Output SPDT relay
Basic electrical insulation 250 VAC (rms)
(contact/electronics)
Contact ratings (AgCdO) µ (micro gap)
Resistive loads AC 1 10 A/250VAC (2500 VA)
DC 1 1 A/250 VDC (250 W)
or 10 A/25 VDC (250 W)
Small inductive loads AC 15 2.5 A/230 VAC
DC 13 5 A/24 VDC
Mechanical life ≥30 x 106operations
Electrical life AC 1 ≥2.5 x 105operations
(at max. load)
Operating frequency ≤7200 operations/h
Insulation voltages
Rated insulation voltage ≥2.0 kVAC (rms) (cont./elec.)
Rated transient protection volt. 4 kV (1.2/50 µs) (cont./elec.)
(IEC 60664)
Function
Output
Type
Power supply
Time range
• Time ranges: 0.15 s to 60 s
• Automatic start after drop out of power supply
• Knob-adjustable time within range
• Repeatability deviation: ≤1%
• Output: 10 A SPDT relay
• Plug-in type module
• Scantimer housing
• LED-indication for supply on
• AC or DC power supply
Delay on Release
Types B 128, B 121
Ordering Key
Product Description
Type Selection
Time Specifications Output Specifications
B 128 220 006
2Specifications are subject to change without notice (25.10.99)
Power ON time ≥200 ms
Indication for
Power supply ON LED, red
Environment
Degree of protection IP 20 B
Pollution degree 2 (IEC 60664)
Operating temperature -20° to +50°C (-4° to +122°F)
Storage temperature -50° to +85°C (-58° to +185°F)
Weight 85 g
Approval UL, CSA
B 128, B 121
Power supply AC types Installation cat. III (IEC 60664)
Rated operational voltage
Through pins 2 & 10 220 220 VAC ±15%,
or pins 2 & 7 45 to 65 Hz
120 120 VAC ±15%,
45 to 65 Hz
024 24 VAC ±15%,
45 to 65 Hz
Dropout tolerance ≥10 ms
Rated insulation voltage None
Rated transient protection volt. 4 kV (1.2/50 µs) @ 220 VAC
2.5 kV (1.2/50 µs) @ 120 VAC
800 V (1.2/50 µs) @ 24 VAC
(line/neutral)
Power supply DC type Installation cat. III (IEC 60664)
Rated operational voltage 724 24 VDC + 15/- 20% (pin 2 pos.)
Rated insulation voltage None
Rated transient protection volt. 800 V (1.2/50 µs)
Consumption AC supply
60 mA @ 50 Hz/70 mA @ 60 Hz
DC supply 1 W
Power supply
B 128
Power supply
B 121
SPDT
8 pin
Knob-adjustable on scale in
seconds.
Power supply
Relay on
The relay operates immedi-
ately after power supply is
applied.
When power supply is inter-
rupted, the time period starts
and at the end of the set time
the relay releases.
If power supply is reapplied
before the relay releases, the
time is reset and the relay
remains on.
B 121/B 128 monitor that
power supply is applied. If
power supply is interrupted,
the relay starts e.g. an alarm
(battery driven) after the time
period has expired.
Please note
B 128 and B 121 should not
be operated by pulses shorter
than 500 ms.
Sockets◊S 408, S 411
Hold down spring◊HF
Mounting rack SM 13
Socket cover BB 4
Potentiometer lock PL 1
For further information refer "Accessories".
Supply Specifications General Specifications
Mode of Operation
Time Setting
Operation Diagram
Wiring Diagrams
Accessories
SPDT
11 pin
