# Example: phase_locking

> Note

> You can launch an interactive, editable version of this example without installing any local files using the Binder service (although note that at some times this may be slow or fail to open):

Phase locking of IF neurons to a periodic input.

    from brian2 import *

    tau = 20*ms
    n = 100
    b = 1.2 # constant current mean, the modulation varies
    freq = 10*Hz

    eqs = '''
    dv/dt = (-v + a * sin(2 * pi * freq * t) + b) / tau : 1
    a : 1
    '''
    neurons = NeuronGroup(n, model=eqs, threshold='v > 1', reset='v = 0',
                          method='euler')
    neurons.v = 'rand()'
    neurons.a = '0.05 + 0.7*i/n'
    S = SpikeMonitor(neurons)
    trace = StateMonitor(neurons, 'v', record=50)

    run(1000*ms)
    subplot(211)
    plot(S.t/ms, S.i, '.k')
    xlabel('Time (ms)')
    ylabel('Neuron index')
    subplot(212)
    plot(trace.t/ms, trace.v.T)
    xlabel('Time (ms)')
    ylabel('v')
    tight_layout()
    show()