Abstract: There are disclosed a method of call control (gapping) and a communications switching system in which such method is implemented, the system incorporating a call gapping arrangement for limiting the recurrence rate of successive call attempts for a particular type of call, for example to a national phone-in number, the arrangement comprising a clock (10) for determining a succession of call gapping intervals; a first up/down counter (18) having a limit N; a signal generator (11) responsive to the clock and coupled to the counter (18) to increment it by a value m each interval; a second up/down counter (21) having a limit M less than N, the counters (18, 21) being responsive to call processing circuitry (14) to be decremented for each call attempt effected by the system: a comparator (15) responsive to the content of counter (21) becoming zero to inhibit the call processing circuitry (14) from allowing call attempts.